Implement optional versioning override version for pinned workflows

[carlydf]

What changed?

Implement optional versioning override version for pinned workflows.
Only for UpdateOptions, not for start-with-override or reset-with-override.

Why?

So that a user can set a Pinned Override on a batch of workflows with different versions (or on a single workflow, but without having to look up and provide the specific version) and simply mean "pin to what you are already on, forever."

Setting a Pinned Override on an already-pinned workflow and not changing the version seems silly, but, with the introduction of the upgrade-on-continue-as-new option, setting a Pinned Override means that, even if the workflow says "upgrade-on-CaN", the workflow will remain on the override version after CaN.

How did you test it?

• built
• run locally and tested manually
• covered by existing tests
• added new unit test(s)
• added new functional test(s)

Potential risks

• None

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Note

Implements implied pinned overrides for workflow option updates and covers them with tests.

• Update service/history/api/updateworkflowoptions/api.go to clone request options and, when a pinned override omits version, auto-fill from the workflow’s effective deployment; return FailedPrecondition if behavior isn’t already pinned. Continue to validate via ValidateVersioningOverride, then merge/apply.
• Add tests: TestUpdateWorkflowExecutionOptions_SetImpliedPinnedSuccess and ..._Error; refactor helpers (startVersionedWorkflow, startUnpinnedWorkflow, setAndCheckOverrideWithExpectedOutput), improve assertions, and set useV32 in suites.
• Extend test utilities with testvars.WithWorkflowID.
• Bump dependency go.temporal.io/api to v1.59.1-0.20260106204414-b9a666f3d64e.

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