lsifstore: add API docs tests
Created by: slimsag
After this change, we have decent test coverage for:
WriteDocumentationSearchPreworkWriteDocumentationPagesWriteDocumentationSearchWriteDocumentationPathInfoWriteDocumentationMappingsdocumentationPathIDToIDdocumentationPathIDToFilePathDocumentationPageDocumentationPathInfoDocumentationDefinitions
It's not perfect - more could be done to improve these, make them more legible, etc. But it's a start, and decent coverage.
Helps #20567
Helps #21938
Signed-off-by: Stephen Gutekanst [email protected]