Add project-scoped compiler feature flags

[timotheeguerin]

Summary

• add project-only features support in tspconfig.yaml with validation for known compiler feature names
• gate internal modifier and function declaration experimental warnings behind compiler feature flags for project code
• add tsp info features to list available compiler features and enabled state

Validation

• pnpm --filter @typespec/compiler test
• pnpm --filter @typespec/compiler build
• pnpm --filter @typespec/compiler lint
• touched-file prettier --check
• pnpm chronus verify

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/compiler@10826

commit: 5047193

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - feature ✏️

Add project-scoped compiler feature flags to tspconfig.yaml. Compiler feature definitions,> are tracked internally with descriptions and can be listed with tsp info features.,> ,> yaml title=tspconfig.yaml,> kind: project,> features:,> - internal-modifier,> - function-declarations,>

[azure-sdk-automation]

You can try these changes here

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