Remove .NET Framework remarks (System namespace)

[gewarren]

.NET Framework API ref has moved to its own repo (https://github.com/dotnet/dotnetfw-api-docs), so we can clean up .NET Framework remarks, exceptions, and code examples out of this repo. Contributes to #12513.

Removes remarks and examples related to:

• .NET Framework versions
• Code-access security
• Configuring apps via app.config file
• App domains

Also removes all remarks from obsolete APIs.

Hide whitespace changes

[Copilot]

Pull request overview

Cleanup of legacy .NET Framework-specific content from xml/System/* ECMAXML files: removes remarks/examples/exceptions about .NET Framework versions, code-access security, app-domain APIs, app.config configuration, and obsolete-API sample code. Part of issue #12513 to prepare docs for backporting to dotnet/runtime triple-slash comments.

Changes:

• Replace ".NET Framework"-qualified wording with version-agnostic ".NET" prose, drop CAS/app.config/app-domain notes, and remove ".NET Framework only" exception entries.
• Wipe remarks on obsolete or framework-only APIs (e.g., NonSerializedAttribute, LoaderOptimization, several AppDomain/AppDomainSetup members).
• Minor formatting cleanup of bullet lists and tables.

Reviewed changes

Copilot reviewed 63 out of 63 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
xml/System/Activator.xml	Removes Framework probing/policy notes; preserves AssemblyLoadContext guidance.
xml/System/AppContext.xml	Drops <AppContextSwitchOverrides> registry/config description.
xml/System/AppDomain.xml	Major cleanup of CAS/app-domain remarks/examples; replaces several remarks with "To be added.". Contains "in call cases" typo.
xml/System/AppDomainSetup.xml	Wipes ApplicationBase/TargetFrameworkName remarks.
xml/System/AppDomainUnloadedException.xml	Drops Framework 2.0 history and examples.
xml/System/Array.xml	Removes gcAllowVeryLargeObjects and Quicksort change notes; leaves garbled trailing text on line 94.
xml/System/ArgumentNullException.xml	Reformats initial-property table; missing closing backtick in Message row.
xml/System/ArraySegment`1.xml	Drops Framework 4.6 IReadOnlyCollection note and bullet blank lines.
xml/System/Attribute.xml	Removes "starting with Framework 2.0" security-attribute notes.
xml/System/BadImageFormatException.xml	Drops Framework version-mismatch example; tightens bullet formatting.
xml/System/CannotUnloadAppDomainException.xml	Bullet whitespace cleanup.
xml/System/Char.xml	Hard-codes Unicode 8.0 classification.
xml/System/Console.xml	Trims "starting with Framework 4" wording.
xml/System/ConsoleCancelEventArgs.xml	Drops 3.5/4 cancel-key history.
xml/System/DateTime.xml	Bulk removal of Framework version-qualifiers across Add*, Parse, ParseExact, To*Time, TryParseExact.
xml/System/DateTimeOffset.xml	Same kind of Framework-qualifier cleanup.
xml/System/DllNotFoundException.xml	".NET Framework assembly" → ".NET assembly".
xml/System/Environment.xml	Removes CER/Framework-only notes; bullet reformatting.
xml/System/Exception.xml	Drops Framework 4.5 HResult-setter note and AppDomain-boundary note.
xml/System/FormatException.xml	Re-indents large bullet block; minor prose updates.
xml/System/GC.xml	Removes <gcConcurrent> config link; ".NET Framework 4.5.1" wording dropped.
xml/System/GenericUriParser.xml	Introduces invalid <xref:System.Uri#remarks>.
xml/System/GenericUriParserOptions.xml	Same invalid xref + Framework note removal.
xml/System/IAsyncResult.xml	Drops "Beginning with Framework 4.5" qualifier.
xml/System/IConvertible.xml	Article title "in the .NET Framework" → "in .NET".
xml/System/ICustomFormatter.xml	Bullet/inline-list cleanup.
xml/System/IFormatProvider.xml	".NET Framework" → ".NET" wording.
xml/System/IFormattable.xml	Similar wording change; introduces ungrammatical "The .NET includes".
xml/System/IntPtr.xml / UIntPtr.xml	Merges .NET 5+ IFormattable sentence into the always-implemented list.
xml/System/InvalidCastException.xml	Article title text update.
xml/System/LoaderOptimization.xml / LoaderOptimizationAttribute.xml	Wipes CAS/multi-domain remarks.
xml/System/LocalDataStoreSlot.xml	Wording + minor reflow.
xml/System/MarshalByRefObject.xml	Removes remoting examples; consolidates PNSE exception entry.
xml/System/Math.xml	Drops "In .NET Core 3.0 and later" qualifier.
xml/System/MethodAccessException.xml	Removes Framework 4 transparency note and "partially trusted code" phrase.
xml/System/NonSerializedAttribute.xml	Replaces full remarks with "To be added."
xml/System/OperatingSystem.xml	".NET Framework" → ".NET" wording.
xml/System/OutOfMemoryException.xml	Removes gcAllowVeryLargeObjects note.
xml/System/PlatformID.xml	Removes ".NET Core" qualifier.
xml/System/Progress`1.xml	Rewords blog link description.
xml/System/Random.xml	Removes Framework seed/Quicksort notes; leaves merge-conflict markers in remarks.
xml/System/ResolveEventArgs.xml / ResolveEventHandler.xml	Drops "Beginning with Framework 4" prefixes.
xml/System/STAThreadAttribute.xml	Reformats COM threading-model table.
xml/System/Single.xml	Bulk Framework-qualifier cleanup across Parse/TryParse; only first row of one table is reformatted.
xml/System/StringComparer.xml	Removes <NetFx45_CultureAwareComparerGetHashCode_LongStrings> mitigation.
xml/System/StringSplitOptions.xml	Removes ".NET 5+ only" qualifier.
xml/System/TimeSpan.xml	Drops Framework-4 formatting history.
xml/System/TimeZone.xml / TimeZoneInfo.xml	Drops Framework 1.x/3.5 comparison notes.
xml/System/Tuple.xml / TupleExtensions.xml	"the .NET Framework" → ".NET" across many remarks.
xml/System/TypeAccessException.xml	Removes transparent-code and MissingMetadataException paragraphs.
xml/System/TypedReference.xml	Removes ReflectionPermission note.
xml/System/Uri.xml	Drops large IRI app.config block, version-history notes; leaves a stray ## header at line 5154.
xml/System/UriBuilder.xml	Consolidates Fragment/Query Framework-vs-.NET-5 paragraphs.
xml/System/ValueType.xml	".NET Framework" → ".NET".
xml/System/Version.xml	Removes NT/Framework 2.0 service-pack note and ".NET Framework only" exceptions.