Don't store full blob path in ES filename field

What does this MR do?

This verifies the changed indexer behaviour from gitlab-elasticsearch-indexer!44 (merged)

We're also renaming the blob-related code to use path rather than filename, to be consistent with the Path field in the ES index, and the intention of this code (which deals with full paths, rather than just filenames).

This also removes the Elasticsearch::Git::LiteBlob class, which isn't used anymore and a leftover from the Ruby indexer which was removed in !15641 (merged)

• Update version for gitlab-elasticsearch-indexer

Ref: #7832 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers