The `leaktest` package detects potential goroutine leaks by snapshotting
the set of goroutines running when `leaktest.AfterTest(t)` is called,
returning a closure, and comparing the set of goroutines when the
closure is called (typically `defer`'d).

A race condition was uncovered in cockroachdb#93849 whereby logging-related
goroutines that are scheduled by an `init` function in
`pkg/util/logging` can sometimes be spawned _after_ the `AfterTest`
function is run. When the test completes and the closure is run, the
test fails due to a difference in the before / after goroutine
snapshots.

This mode of failure is deemed to be a false-positive. The intention of
the logging goroutines are that they live for the duration of the
process. However, exactly _when_ the goroutines scheduled in the `init`
functions actually start run, and hence show up in the goroutine
snapshots, is non-deterministic.

Exclude the logging goroutines from the `leaktest` checks to reduce the
flakiness of tests.

Closes cockroachdb#93849.

Release note: None.