feat(pubsub): add enabled option to HedgingOptions (post-merge adjustments)

[feywind]

Overview

This is a tentative standalone (unstacked) catch-all PR on top of Stack #9467 (#9462-#9466, #9635-#9636) for post-merge adjustments to Publish Hedging in @google-cloud/pubsub.

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Summary of Changes in This PR

• HedgingOptions.enabled (handwritten/pubsub/src/publisher/hedging.ts, handwritten/pubsub/src/default-options.ts):
  • Adds enabled?: boolean to HedgingOptions and defaultOptions.publish.hedging.enabled = true, aligning with the cross-language hedging settings surface (enabled: true, hedgeDelay: 1000ms (1s), maxTokens: 50, refillRatio: 0.1 with bounds 100ms..10s, 1..250, 0.001..0.2).
  • Returning undefined from HedgingTokenBucket.validateAndResolveHedgingOptions when hedging.enabled === false allows callers to explicitly disable hedging via {enabled: false}.
• Unit & System Tests (handwritten/pubsub/test/publisher/hedging.ts, handwritten/pubsub/system-test/hedging.test.ts):
  • Added unit and system test assertions verifying hedging: {enabled: false} disables hedging and hedging: {} defaults enabled to true.

[gemini-code-assist]

Code Review

This pull request introduces an enabled flag to the publish hedging options, allowing users to explicitly enable or disable hedging. It updates the default options, the HedgingOptions and ResolvedHedgingOptions interfaces, and the validation logic to respect this flag. It also adds corresponding unit and system tests. The feedback suggests making the enabled property in ResolvedHedgingOptions required rather than optional, as it is always returned as true when the options are successfully resolved.

[gemini-code-assist]

Since validateAndResolveHedgingOptions always returns { enabled: true, ... } when hedging is enabled, and returns undefined otherwise, the enabled property in ResolvedHedgingOptions will always be present and true. It should be defined as a required boolean (readonly enabled: boolean;) rather than optional to avoid unnecessary null/undefined checks for consumers of ResolvedHedgingOptions.

Suggested change

	readonly enabled?: boolean;
	readonly enabled: boolean;