Jdb/refactor inline diff table row

What does this MR do?

For: #236071 (closed)

Refactors DiffTableCell directly into InlineDiffTableRow. This is to reduce the number of components created in the MR diffs tab.

In preliminary testing this reduced initial load time ~40% from ~5 seconds to ~3 seconds on my local machine.

NOTE: This is the first of a series of MRs to address the performance issues with merge requests. I have only updated the inline version of MR diffs here to reduce the size of the change. This introduces some complexity and some duplication of code but is a necessary iterative step to get to a unified non-table based layout.

👉 We are here

1. 👉 Move diff_table_cell logic into inline_diff_row !40906 (merged)
2. Move diff_table_cell logic into parallel_diff_row & remove diff_table_cell
3. Extract shared logic and duplicated code from parallel/inline_diff_row into utility file
4. Add non-HTML table layout version of diff_row behind feature flag
5. Remove parallel/inline_diff_row components and feature flag

Screenshots

n/a

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content