Test 'oxlint' in the Authoring MFE

[bradenmacdonald]

I'd like us to consider replacing eslint with oxlint across all Open edX frontend repos. This ticket is to track work to test Oxlint in this MFE's codebase. See the related PRs for findings.

PR to use oxlint: TBD

Issues found from testing

• 104 missing/spurious await statements in test code test: fix test code improperly using/missing 'await' #2560
• 22 additional missing/spurious await statements chore: fix incorrect or missing 'await' usages #2592
• 8 redundant declarations of undefined type on optional parameters chore: fix unnecessary 'undefined' types #2589
• 110 unused error variables chore: don't name unused errors in catch expressions #2591
• 15 questionable .toString() usages chore: fix no-base-to-string #2597
• many more - haven't updated this yet.