[Popover][Menu][Select] Remove deprecated props

[siriwatknp]

Summary

Remove all deprecated props from the Popover component.

Breaking change

The following deprecated props have been removed:

• BackdropComponent — use slots.backdrop instead
• BackdropProps — use slotProps.backdrop instead
• PaperProps — use slotProps.paper instead
• TransitionComponent — use slots.transition instead
• TransitionProps — use slotProps.transition instead

 <Popover
-  BackdropComponent={CustomBackdrop}
-  BackdropProps={{ invisible: true }}
-  PaperProps={{ elevation: 12 }}
-  TransitionComponent={CustomTransition}
-  TransitionProps={{ timeout: 500 }}
+  slots={{ backdrop: CustomBackdrop, transition: CustomTransition }}
+  slotProps={{
+    backdrop: { invisible: true },
+    paper: { elevation: 12 },
+    transition: { timeout: 500 },
+  }}
 />

Changes

• Removed all 5 deprecated props from source, types, and PropTypes
• Simplified externalForwardedProps — no longer merges deprecated props
• Removed unused elementTypeAcceptingRef import
• Migrated all tests from deprecated to slot API
• Updated Popover.spec.tsx type tests
• Added PaperProps as deprecated prop to Menu.d.ts (Menu inherited it from Popover — needed to keep Menu working until its own deprecated props are removed)
• Added migration guide entry in upgrade-to-v9.md
• Regenerated API docs

Test plan

• pnpm prettier passes
• pnpm eslint passes
• pnpm typescript passes
• pnpm test:unit Popover passes (83 tests)

[mui-bot]

Netlify deploy preview

• docs/data/material/migration/upgrade-to-v9/upgrade-to-v9.md

Bundle size report

Bundle	Parsed size	Gzip size
@mui/material	▼-448B(-0.09%)	▼-176B(-0.12%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

Generated by 🚫 dangerJS against 68f2b3e

[mj12albert]

Looks good ~ there's a small cleanup that could be included in this PR as well: https://github.com/siriwatknp/material-ui/blob/master/packages/mui-material/src/Menu/Menu.js#L220-L223

[siriwatknp]

@mnajdova @mj12albert I have to do the removal of Menu in this PR because it's affected by the Popper change. As well as SelectInput because it's using Menu internally.