Revert "Merge branch '118442-restyle-changes-header-and-file-tree' into 'master'"

What does this MR do?

This MR reverts !22364 (merged) which introduced a number of regressions in the Web IDE:

• #197493 (closed)
• #198002 (closed)
• #198029 (closed)
• #198057 (closed)

Screenshots

Description	Screenshot on f0bb99d0
👍 Nested dropdown not showing is fixed.
👍 Duplicate changed icons showing is fixed.
👍 Changed icon in tab alignment is fixed.
👍 Delete status icon persisting after discard is fixed.
MR UX enhancements are reverted.