Isolate plist reading and writing in the host's plist module

[kraenhansen]

Closes #472. bplist-parser support in readAndParsePlist already landed in 14e5119; this does the remaining part of the issue — sharing it with verify-prebuilds — and isolates plist handling so @expo/plist and bplist-parser are easier to update.

• readAndParsePlist moves into packages/host/src/node/plist.ts and is exported from the Node.js entrypoint (not from cli/apple.ts, which would make the entrypoint load @bacons/xcode and the CLI utilities). verify-prebuilds.mts uses it instead of its own copy, and node-addon-examples drops its @expo/plist and bplist-parser devDependencies.
• The XML write helper from prebuilds/apple.ts moves alongside it as writePlist (internal) and also backs the two Info.plist writers in cli/apple.ts. plist.ts is now the only module importing either library.
• plist.ts is format-only; Info.plist semantics stay with the callers' zod schemas. readAndParsePlist still returns unknown — callers validate.

Test plan

• pnpm run build, lint, prettier:check; host tests (67) and cmake-rn tests (16)
• Built the node-addon-examples for arm64;x86_64-apple-ios-sim and ran verify: 13 prebuilds verified, reading binary plists through the shared helper
• Ran createAppleFramework on a test dylib (flat and versioned): both write the expected XML Info.plist through writePlist
• CI

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