Introduce implementation for FileType

[brkyvz]

Rationale for this change

Introduces the reference implementation for the new LogicalTypeAnnotation File as discussed in this design document

What changes are included in this PR?

Introduces a new LogicalTypeAnnotation called FILE. It enforces that a group with this type annotation have the following fields by name:

path 		 		STRING	NOT NULL
size	 	 		INT64			
offset				INT64      	
etag				STRING

Are these changes tested?

Yes, unit tested

Are there any user-facing changes?

Introduces a new LogicalTypeAnnotation called FILE