fix(field): fix z-index issues of tooltip and revert dialog

[mariuslundgard]

Description

• The poppers (dialog and tooltip) in @sanity/field now use the LegacyLayerProvider to set the z-offset to a higher number than the poppers in the @sanity/form-builder.
• This fixes the issues by making sure that the revert changes dialog is always on top of the form builder, even when viewing a deeply nested array item.

What to review

• Open a document with deeply nested array items (2 level or deeper).
• Edit a field in a deeply nested array item.
• Click the Revert changes button below the changed field, and make sure the dialog is available (on both wide and narrow screens).

Notes for release

• Fixes a z-index issue with revert changes dialogs.

[vercel]

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test-studio – ./

🔍 Inspect: https://vercel.com/sanity-io/test-studio/Fj4NZdFdwnBUdZycyHyCmnZmavxz
✅ Preview: https://test-studio-git-bug-ch8188field-poppers-z-index.sanity.build

perf-studio – ./

🔍 Inspect: https://vercel.com/sanity-io/perf-studio/9Lp3nvDvNgPSKETHkcTwh3zAuG8R
✅ Preview: https://perf-studio-git-bug-ch8188field-poppers-z-index.sanity.build

[bjoerge]

LGTM!