feat: add elevation tokens and fix Android dp spec bug

[adrcotfas]

Motivation

Part of the foundation of adding tokens and structure.

Add theme.elevation sys token and clean up elevation types

Replace the ElevationLevels numeric enum with an ElevationLevel string union, add ThemeElevation and theme.elevation.level0-5 as a proper sys token (matching md.sys.elevation.* spec naming), export elevationInputRange as the single source of truth for the [0-5] interpolation range, fix iOS shadow color to read from
theme.colors.shadow instead of a hardcoded #000, and remove ELEVATION_LEVELS_MAP from Menu in favor of the template literal pattern already used in Surface.

Related issue

See https://www.notion.so/callstack/React-Native-Paper-Foundation-for-MD3-Expressive-34c5d027c0f880edba3df107cd35946f?source=copy_link

Merge order:

• refactor: remove MD3 prefix and use deprecated aliases #4910

• refactor: move styles/ into src/theme/ tree #4915

• refactor: add color role table and buildScheme #4916

• feat: add theme.state opacity tokens and split theme types #4917

• feat: add theme.shapes and cornersToStyle #4919

• feat: add emphasized typescale and fix letter-spacing spec bugs #4920

• feat: add motion tokens (spring, easing, duration) #4922

• feat: add elevation tokens and fix Android dp spec bug #4923

  Test plan

  • yarn typescript -- no new type errors
  • yarn test -- all tests pass

[github-actions]

The mobile version of example app from this branch is ready! You can see it here.