Make the background IP Rule-refreshing goroutine exit on server shutdown

[iain-macdonald]

No description provided.

[Copilot]

Pull request overview

This PR ensures the background IP rules cache-refreshing goroutine terminates during server shutdown, avoiding lingering goroutines in long-running enterprise servers.

Changes:

• Add a shutdown handshake (stop/done) for the IP rules refresher and register it with the server HealthChecker.
• Add a goroutine-leak regression test using go.uber.org/goleak.
• Wire new dependencies through Go modules and Bazel.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
go.mod	Adds go.uber.org/goleak dependency for goroutine leak testing.
enterprise/server/ip_rules_enforcer/ip_rules_enforcer_test.go	Adds a goleak-based test asserting the refresher stops on shutdown.
enterprise/server/ip_rules_enforcer/ip_rules_enforcer.go	Implements stoppable refresher goroutine and HealthChecker shutdown integration.
enterprise/server/ip_rules_enforcer/BUILD	Adds Bazel deps for proto and goleak.
deps/go_deps.MODULE.bazel	Exposes org_uber_go_goleak repo for Bazel builds.

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[vanja-p]

nit: you can make this a bit neater by doing:

closeStop := sync.OnceFunc(func() {close(stop)})

Then you can just call pass that to shutdownRefresher, instead of passing both stop and shutdownOnce. Or you can even just call closeStop() before calling shutdownRefresher, since it's pretty weird to pass in a function just to call once it right away. Then maybe shutdownRefresher should be called waitForShutdown.

[iain-macdonald]

Good idea, fixed