fix(formatter): fix formatting order in codeActionsOnSave

[panudetjt]

Note

AI Assisted writing

Summary

• Use onWillSaveTextDocument to apply formatting edits before code actions on save are collected, guaranteeing format→lint
  ordering when both source.format.oxc and source.fixAll.oxc are configured
• Suppress the source.format.oxc code action when configured in codeActionsOnSave to prevent double-formatting (the code action's editor.action.formatDocument command would run after lint fixes, undoing them)

Problem

Previously, source.format.oxc was implemented as a code action with a command. VS Code collects all code actions before applying any of them, so lint fix edits were computed on the original (unformatted) document. When the format command ran after lint fixes, it could undo lint edits that also changed formatting (e.g. unicorn/number-literal-case uppercasing hex literals).

Test plan

• Verify source.format.oxc code action is suppressed when source.format.oxc is in codeActionsOnSave
• Verify source.format.oxc code action is still returned for manual use when not in codeActionsOnSave
• Manual: configure source.format.oxc and source.fixAll.oxc in codeActionsOnSave, save a file with both formatting and
  lint issues, verify format runs first

[Sysix]

Sorry for the long wait 🙇
I did not have time to check this PR, I am afraid of spamming the LSP server, need to check if creates some performance problems. 🙏

[panudetjt]

I'm not sure either! 😂
This is my first contribution to a VS Code extension, so I would be very grateful if you could guide me through the process.
Thank you