fix(ui): prevent autosave from reverting recently edited fields

[lucasvass1]

Fixes #17676

Summary

• Autosave could overwrite recently typed field values: switching to a different field while a previous autosave request was still in flight cleared that field's "modified" protection, so the stale response (with an older/partial value) could land and overwrite the newer edit. Fixed by tracking a per-field modifiedAt timestamp and comparing it against when each request was sent — a response is only accepted for a field if no local edit happened to it after that specific request was dispatched.
• Media library (and any relationship/upload) list drawer would flicker/reload during editing: unmodified object/array-valued fields (relationship, upload) got a brand new, content-identical value reference on every accepted autosave merge, which cascaded into useListDrawer recomputing and remounting the open drawer. Fixed by preserving the existing reference in mergeServerFormState when the incoming value is deeply equal to the current one.

Test plan

• Added an e2e regression test reproducing the reported race (type in one field, switch to another before autosave completes) - fails without the fix, passes with it
• Added an e2e test asserting an open relationship list drawer isn't remounted by an unrelated autosave - fails without the fix, passes with it
• Added a unit test in mergeServerFormState covering reference preservation for content-identical values
• Existing autosave/computed-field tests in test/form-state still pass (no regression to the "don't overwrite a field being actively edited" behavior)
• pnpm run build:core and lint pass

[jacobsfletch]

@lucasvass1 I think this may already be fixed by #17455. Would you mind testing that PR to confirm?

[lucasvass1]

@jacobsfletch oi, tudo bem? Analisei a PR #17455 e ela corrige um dos erros que corrigi, porém não o segundo.

Ela resolve a sobrescrita de campo por resposta de autosave obsoleta (digitar em um campo, trocar pra outro antes do autosave anterior terminar, e o valor reverter).

Mas não resolve a media library recarregando/piscando durante o autosave. Isso acontece porque, mesmo quando um campo relationship/upload não foi editado, o merge da PR aceita o valor vindo do servidor como se fosse novo — e como esse valor chega recém-serializado a cada resposta, ele tem uma referência diferente mesmo com o mesmo conteúdo. Isso faz o drawer da lista recalcular e remontar sem necessidade.

Testei isso na prática, rodando meus testes contra o branch da #17455: o teste da sobrescrita passa, mas o teste do remount do drawer falha.