fix: make TestWaitExecHandleHooks deterministic for 2-container hook ordering

[lubronzhan]

Summary

Observed a flaky test from this PR #9943

• Fixes a flaky test in TestWaitExecHandleHooks: "should return no error with 2 spec hooks in 2 different containers, 1st container starts running after 10ms, 2nd container after 20ms, both succeed"
• Root cause: the informer's DeltaFIFO queue coalesces rapid source.Modify calls, delivering only the latest pod state to the handler before the first hook fires — so the mock was called with resourceVersion:3 (both containers running) instead of the expected resourceVersion:2 (container1 running, container2 waiting)
• Fix: introduce waitForSignal chan struct{} on change and onCalled func() on expectedExecution to synchronize the goroutine emitting changes with hook execution, making the test 100% deterministic

Observed failure

CI run: https://github.com/velero-io/velero/actions/runs/28119573625/job/83267758421

mock: Unexpected Method Call
ExecutePodCommand(..., resourceVersion:"3", container2: running, ...)

The closest call I have is:
ExecutePodCommand(..., resourceVersion:"2", container2: waiting, ...)

The comment "Each of these states will be seen by the UpdateFunc handler" was incorrect — under load the FIFO can skip intermediate states.

Test plan

• Run go test ./internal/hook/... -run TestWaitExecHandleHooks -count=20 — all pass
• No production code changed, test infrastructure only

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🔨 Latest commit	f624362

[Copilot]

Pull request overview

This PR makes TestWaitExecHandleHooks deterministic by synchronizing pod state transitions with hook execution to avoid informer update coalescing that can skip intermediate pod states, eliminating a known flake in the 2-container hook ordering scenario.

Changes:

• Adds channel-based synchronization (waitForSignal / onCalled) to control when subsequent fake pod updates are emitted.
• Updates test comments to reflect informer coalescing behavior.
• Adds an unreleased changelog entry describing the flaky-test fix.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/hook/wait_exec_hook_handler_test.go	Introduces synchronization hooks to make the flaky 2-container ordering test deterministic.
changelogs/unreleased/9944-lubronzhan	Documents the test flake fix in the unreleased changelog.

Comments suppressed due to low confidence (1)

internal/hook/wait_exec_hook_handler_test.go:743

• waitForSignal can deadlock the test indefinitely if the expected hook never fires (e.g., a regression prevents ExecutePodCommand from being invoked), because the pod-update goroutine blocks forever and prevents later state transitions. Add a bounded wait (or tie it to context cancellation) so failures fail fast instead of hanging the entire test run.

				Result(),
			groupResource: "pods",
			byContainer: map[string][]PodExecRestoreHook{
				"container1": {
					{

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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