feat(typescript-angular): add withHttpResource option for signal-based GET resources

[thekhegay]

Adds an opt-in withHttpResource option to typescript-angular (Angular 20+; a lower ngVersion is refused).

Every GET operation without a request body gets a <operationId>Resource method next to its Observable method, returning an Angular HttpResourceRef:

readonly pet = inject(PetService).getPetByIdResource(() => ({ petId: this.petId() }));

• Returning undefined, or leaving a required parameter null/undefined, keeps the resource idle.
• JSON responses use httpResource, text httpResource.text, binary httpResource.blob, chosen at generation time the same way selectHeaderAccept does.
• The query/header/auth code moved into a shared partial, so the param codec, credentials (read reactively), Accept, withCredentials, context and transferCache behave exactly like the Observable methods.
• Options: defaultValue, injector, equal, debugName, context, transferCache.
• Left out on purpose: writes (Angular recommends resources for reads only), GETs with a body, observe, httpHeaderAccept, parse, and resource signatures in the *Interface files.

With the option off the output is unchanged: regenerating every bin/configs file gives zero diff. Tested with Java unit tests and a new sample build (typescript-angular-v22-provided-in-root/builds/with-http-resource) with an HttpTestingController spec; the generated code was also compiled and run against Angular 20, 21 and 22.

Closes #21263. Related: #22537 — this keeps the Observable methods and doesn't touch existing samples.

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  Commit all changed files.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

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Summary by cubic

Adds an opt-in withHttpResource option to typescript-angular that generates signal-based <operationId>Resource methods next to the existing Observable methods. With the option off, generated output is unchanged; enabling it requires Angular 20+ and rejects lower ngVersion values.

New Features

• Every GET without a request body gets a <operationId>Resource method returning an Angular HttpResourceRef; JSON, text, and binary responses use httpResource, httpResource.text, and httpResource.blob.
• The resource stays idle while the params function returns undefined or a required parameter is null/undefined.
• Query, header, auth, withCredentials, context, and transferCache behavior matches the Observable methods.
• Supports defaultValue, injector, equal, debugName, context, and transferCache.
• Methods whose names would collide with another operation are skipped with a generation-time warning.
• Non-GET operations, GETs with a request body, observe, httpHeaderAccept, and parse remain Observable-only.

Closes #21263.

^{Written for commit a344b41. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 36 files

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[thekhegay]

About cubic review:

• README collision note and null/undefined spec case: fixed in a344b41.
• git_push.sh and query.params.ts: these come from the shared templates every sample uses, so changing them here would change the output of every generator. Out of scope for this PR.
• Options-only overload for GETs whose params are all optional: kept (params?, options?). Telling a params function from an options object at runtime would add a dispatch branch for a case getFooResource(undefined, { ... }) already covers.