ref(forms): Migrate highlights settings

[priscilawebdev]

Replace the legacy highlights JsonForm with AutoSaveForm text areas for tags and context.

This keeps the existing autosave behavior, preserves the project cache updates,
and tightens the tests around the autosave requests.

closes https://linear.app/getsentry/issue/DE-1251/migrate-eventshighlightshighlightssettingsformtsx-from-legacy-form

[linear-code]

DE-1251

[github-actions]

📊 Type Coverage Diff

Metric	Before	After	Delta
Coverage	93.56%	93.56%	±0%
Typed	135,613	135,621	🟢 +8
Untyped	9,336	9,336	±0

🔍 3 new type safety issues introduced

Type assertions (as) (3 new)

File	Line	Detail
static/app/components/core/form/autoSaveForm.tsx	208	as never — { [name]: {message: t('Failed to save')}, } as never
static/app/components/core/form/autoSaveForm.tsx	218	as never — {[name]: true} as never
static/app/components/core/form/autoSaveForm.tsx	224	`as Record<

    TFieldName,
    SchemaOutput<TSchema>[TFieldName]
  >` — `parsedValue.data as Record< TFieldName, SchemaOutput<TSchema>[TFieldName] >` |

This is informational only and does not block the PR.

[TkDodo]

could we re-use the schema here instead of doing another manual JSON.parse ?

[priscilawebdev]

Agreed in principle ....and I tried this. To re-use the schema we need AutoSaveForm to apply the transform on submit (so mutationFn receives the parsed output instead of the raw form value). This required a lot of changes in other files (PR is updated)... What is your take on this?

[TkDodo]

lots of unrelated formatting changes here

[TkDodo]

we can also use passthrough to allow arbitrary values