Add test coverage of rails_info config/version fields for all reconciliation scenarios

Description

This is part 2 of Properly handle full and partial sync (#397702 - closed), to write a test covering all the possible reconciliation scenarios.

• Implementation MRs:
  • Add test coverage of rails_info reconciliation ... (!117136 - merged)
  • Add more test coverage for reconciliation scena... (!117761 - merged)
• Documentation MR: Add information about workspace updates (gitlab-org/remote-development/gitlab-remote-development-docs!21 - merged)
• Docs: https://gitlab.com/gitlab-org/remote-development/gitlab-remote-development-docs/-/blob/main/doc/workspace-updates.md

Follow-up issue: Finish incomplete work on state management logi... (#407518)

Why

Context - #396423 (comment 1316886168)

Modeling of different scenarios that can occur for Partial Sync

https://gitlab.com/gitlab-org/remote-development/gitlab-remote-development-docs/-/blob/main/doc/workspace-updates.md