Refactor spanner-staging-tests and rectify InformationSchemaScannerIT

[aasthabharill]

b/531449982

This PR refactors the Spanner staging integration test pipeline to dynamically adapt to different testing environments (Production, Staging, Cloud-devel). It improves pipeline visibility in GitHub Actions and ensures test reliability across Spanner hosts with differing multi-region provisioning.

Changes and Intent

1. Added a dynamic run-name expression in .github/workflows/spanner-staging-tests.yml

Because this workflow runs against three different Spanner hosts (Prod, Staging, Cloud-devel), distinguishing the runs in the GitHub Actions UI was difficult. Test runs will now clearly identify their target environment (e.g., "Spanner Cloud-devel Integration Tests").

2. Removed the explicit spannerHost input configuration from the pull_request block to avoid masking defaults

• pull_request triggers don't accept the inputs parameter - so the workflow that this PR triggered had no Spanner host set, which is incorrect. (Workflow link)
• Added fallback to cloud-devel URL in the job env block to rectify this issue

3. Added a spannerMultiRegion input parameter to the workflow.

• The default value is dynamically inferred based on the spannerHost: it defaults to nam-private1 for staging, and falls back to nam3 for all other environments.
• Added a new --it-spanner-multi-region flag to the Go test wrappers (it-flags.go, run-spanner-staging-it-tests/main.go) to pass the environment variable down to Maven as a system property.
• Updated InformationSchemaScannerIT.java to construct the SpannerResourceManager using System.getProperty("spannerMultiRegion", "nam3") instead of hardcoding specific multi-regions or relying on custom instance partitions.

Intent:

• Previously, multi-region identifiers like nam3 were hardcoded inside the Java tests.
• Because nam3 is not universally provisioned across all our test environments (like Staging), tests would fail depending on the host.
• Managing this in the CI/CD orchestration layer ensures the correct multi-region is always provisioned for the target host without requiring code changes.

4. Changed PARTITION_ID to default instead of creating a new one

• When a spanner instance is created, Spanner implicitly provisions a built-in partition named "default" that shares the instance's region configuration.
• Spanner strictly prohibits creating a new custom instance partition that shares the exact same region as another partition - so we can't use the spanner instance region due to the default partition that was created
• Therefore, to successfully create a custom partition, the base instance must be created in one configuration (e.g., nam3), and the custom partition must be created in a different configuration (e.g., nam6).
• But across our three environments (Prod, Pre-Prod, and Cloud-devel), there isn't a universally shared set of two distinct multi-region configurations.
• So we will utilize the default partition instead of provisioning a secondary partition.

Tests

• Verified that the run name dynamically changes depending on the Spanner Host passed.
• Verified that the correct multi-region is used when explicitly configured.
• Verified that the correct default multi-region configured for each of the environments is used in the absence of passing one explicitly.
• Verified that the Github "Run workflow" option now shows Spanner Multi-region as a configurable parameter.
• This PR triggers the Spanner Staging Tests. The test correctly used the cloud-devel spanner host URL.

https://screenshot.googleplex.com/4Ew96Vt3ckq9mnh.png

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.68%. Comparing base (06d6601) to head (40fbc16).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4017      +/-   ##
============================================
- Coverage     55.70%   55.68%   -0.03%     
+ Complexity     7235     6782     -453     
============================================
  Files          1124     1124              
  Lines         68447    68447              
  Branches       7721     7721              
============================================
- Hits          38128    38114      -14     
- Misses        27844    27858      +14     
  Partials       2475     2475              

Components	Coverage Δ
spanner-templates	87.66% <ø> (ø)
spanner-import-export	68.57% <ø> (-0.11%)	⬇️
spanner-live-forward-migration	89.29% <ø> (ø)
spanner-live-reverse-replication	83.46% <ø> (ø)
spanner-bulk-migration	92.48% <ø> (ø)
gcs-spanner-dv	88.55% <ø> (ø)
see 6 files with indirect coverage changes

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