feat(gax): retry start upload call and rename ResumableUploadCallSettings to ResumableUploadOptions

[blakeli0]

Stacked PRs:

• ➡️ PR 1 (gax-java): feat(gax): retry start upload call and rename ResumableUploadCallSettings to ResumableUploadOptions #14509 (this PR)
• PR 2 (gapic-generator-java & java-showcase): feat(generator): use UnaryCallSettings and ResumableUploadOptions for resumable uploads #14510 (stacked on feat/resumable-upload-start-retry)

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Summary

• Rename ResumableUploadCallSettings to ResumableUploadOptions: Decouples per-RPC invocation options (chunkSize and globalTimeout) from method-level CallSettings so ResumableUploadOptions is strictly passed per-call to ResumableUploadCallable.futureCall(...) / resumeCall(...) and convenience upload methods.
• Accept UnaryCallSettings in Callables.resumableUpload, HttpJsonCallableFactory.createResumableUploadCallable, HttpJsonResumableUploadClient.create, and ResumableUploadStartCallable.create: Uses UnaryCallSettings<RequestT, ?> in HttpJsonResumableUploadClient and ResumableUploadStartCallable (without extra overloads) and configures retryable codes and retry settings for the initial start upload HTTP call (X-Goog-Upload-Command: start).
• Retry ResumableUploadStartCallable: Wraps the raw ResumableUploadStartCallable in HttpJsonExceptionCallable (with callSettings.getRetryableCodes()) and Callables.retrying(callable, callSettings, clientContext) so transient failures during session initiation are retried automatically.
• Default globalTimeout from UnaryCallSettings: Callables.resumableUpload derives the default ResumableUploadOptions globalTimeout from callSettings.getRetrySettings().getTotalTimeoutDuration().

Related PRs

• Part 2 (GAPIC Generator & Showcase): feat(generator): use UnaryCallSettings and ResumableUploadOptions for resumable uploads #14510

[gemini-code-assist]

Code Review

This pull request refactors the resumable upload configuration by replacing ResumableUploadCallSettings with ResumableUploadOptions for invocation-level options, and utilizing standard UnaryCallSettings for method-level settings. This change simplifies the settings hierarchy and affects client generation, stub settings, and the HTTP/JSON transport layer. The review feedback suggests enhancing type safety in HttpJsonResumableUploadClient and ResumableUploadStartCallable by replacing wildcard generic types with specific type parameters matching the request and response types.

[gemini-code-assist]

Using UnaryCallSettings<RequestT, ResponseT> instead of the wildcard UnaryCallSettings<?, ?> improves type safety by ensuring that the call settings match the request and response types of the client.

Suggested change

	UnaryCallSettings<?, ?> callSettings) {
	UnaryCallSettings<RequestT, ResponseT> callSettings) {

[gemini-code-assist]

Using UnaryCallSettings<RequestT, ResponseT> instead of the wildcard UnaryCallSettings<?, ?> improves type safety by ensuring that the call settings match the request and response types of the client.

Suggested change

	UnaryCallSettings<?, ?> callSettings) {
	UnaryCallSettings<RequestT, ResponseT> callSettings) {

[gemini-code-assist]

Using UnaryCallSettings<RequestT, ?> instead of UnaryCallSettings<?, ?> binds the request type of the settings to the request type of the callable, improving type safety.

Suggested change

	UnaryCallSettings<?, ?> callSettings) {
	UnaryCallSettings<RequestT, ?> callSettings) {