Ensure regenerated modular package.json includes @azure/core-util runtime dependency

[Copilot]

Some generated modular clients import uint8ArrayToString/stringToUint8Array from @azure/core-util, but the migration/update path for existing package.json did not guarantee that dependency was added.

• Problem scope

  • New package generation already handled Azure modular dependency injection, but updatePackageFile-based regeneration could miss runtime deps required by generated models/helpers.

• Generator update: include @azure/core-util in modular update flow

  • Updated packages/typespec-ts/src/index.ts so modular package updates add @azure/core-util (Azure flavor) in the same dependency bundle used during package migration updates.

• Package updater enhancement: merge caller-provided dependencies

  • Updated packages/rlc-common/src/metadata/buildPackageFile.ts:
    • updatePackageFile(...) now accepts dependencies in options.
    • Added dependency updates to early-return conditions.
    • Merges provided dependencies into existing packageInfo.dependencies instead of ignoring them.

• Focused regression coverage

  • Added integration test in packages/rlc-common/test/integration/packageJson.spec.ts verifying updatePackageFile(...) preserves existing deps and merges new ones like @azure/core-util.

const packageFileContent = updatePackageFile(model, initialPackageInfo, {
  dependencies: {
    "@azure/core-util": "^1.9.2"
  }
});