fix: preserve Map keys during finalization and patch replay

[snooze26h]

This PR proposes a fix for a few Map-key cases in draft finalization and patch replay. They reproduce in Immer 11.1.21 and on main at 8848a5b:

• Updating an entry keyed by undefined leaves a revoked draft in the result.
• Replaying a nested patch through a null, boolean, object, or symbol key fails because the path walker converts the key to a string.
• Adding, replacing, or removing an entry with an array key splits that key into multiple patch-path segments.

For example:

import {enableMapSet, produce} from "immer"

enableMapSet()
const base = new Map([[undefined, {count: 0}]])
const next = produce(base, draft => {
  draft.get(undefined).count++
})
next.get(undefined).count // Throws: proxy has been revoked

The patch identifies child drafts by their parent relationship, preserves Map keys during path traversal, and appends each assigned key as a single path segment. The existing object/array prototype-pollution guards are retained, with regression coverage for reserved attributes below Map entries.

Related background: #952 and #1025 addressed numeric Map keys.

Validation

Node.js 24.20.0, macOS arm64, Yarn 1.22.22 via Corepack:

• 64 new tests covering produced values, patch replay and undo, key identity, structural sharing, removed/replaced children, and both auto-freeze modes. 48 regression cases were demonstrated failing before the fix.
• yarn test: 3,900 source tests and 3,349 production-build tests passed; Flow reported 0 errors. Each suite retains 8 pre-existing skips.
• yarn coverage and the existing yarn test:perf scripts completed successfully.
• Prettier checks for the changed files and git diff --check passed.
• A separate public-API reproduction fails on the published package and passes against the patched production build.

I'd appreciate any feedback on the approach or test coverage, and I'm happy to make adjustments. Thanks for taking a look.