feat!: clearer bzlmod extension API for TypeScript toolchains

[jbedard]

Rename the module extension surface so a MODULE.bazel reads self-documenting:

    ts = use_extension("@aspect_rules_ts//ts:extensions.bzl", "typescript")
    ts.toolchain(version = "5.6.2")   # or version_from = "//:package.json"
    use_repo(ts, "npm_typescript")

• Extension symbol ext -> typescript, matching rules_js's convention of naming the extension after its domain concept rather than a generic "ext".
• Tag class deps -> toolchain: the tag selects the TypeScript compiler version backing the toolchain; it does not declare dependencies.
• Attrs lose their redundant ts_ prefix inside the typescript.toolchain
  context: ts_version/ts_version_from/ts_integrity ->
  version/version_from/integrity.

The default repo name npm_typescript and the multi-toolchain name escape hatch are unchanged. The internal npm_dependencies repo rule (shared with the WORKSPACE path) is untouched.

Fix #941

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): yes
• Suggested release notes appear below: yes

BREAKING CHANGES:

The bzlmod module extension API has changed. Update MODULE.bazel:

before

    rules_ts_ext = use_extension("@aspect_rules_ts//ts:extensions.bzl", "ext")
    rules_ts_ext.deps(ts_version = "5.6.2")
    use_repo(rules_ts_ext, "npm_typescript")

after

    ts = use_extension("@aspect_rules_ts//ts:extensions.bzl", "typescript")
    ts.toolchain(version = "5.6.2")
    use_repo(ts, "npm_typescript")

Renames:

• use_extension(..., "ext") -> use_extension(..., "typescript")
• .deps(...) -> .toolchain(...)
• ts_version -> version
• ts_version_from -> version_from
• ts_integrity -> integrity

The local variable bound to use_extension (commonly rules_ts_ext) is arbitrary and may be named anything; the examples now use typescript. The npm_typescript repo name and the name attribute for registering additional TypeScript versions are unaffected.

Test plan

• Covered by existing test cases

[thesayyn]

does this mean we have a typescript toolchain now?

[jbedard]

I guess it's not actually a toolchain, so we could potentially (for now) stick with the .deps() name? That also reduces the breaking change.

Regarding toolchains... see #951 - we can debate the correctness there, but maybe we should also wait till then to do this rename?

[thesayyn]

eh i am fine with breaking changes, i was just curious. i'd be happy to see #951 land honestly. so that we can use configurability and platforms and toolchains to configure typescript in the graph.