kv: Fix test to correctly test the SystemClass

[andrewbaptist]

Previously this test had several issues that are all addressed.
First the system range it was writing to only had a single replica, so
even if it was correctly written to, a network partition wouldn't test
anything. Additionally, the address it was attempting to write to was
a lease change, which is not in the system range. The reason this worked
previously is that there was an early exist from the change lease code
if the old and new leaseholders were the same, so it didn't actually
attempt to write to the leaseholder name at all.

This change addresses all this, but writing to a key in the liveness
range and first replicating the liveness range to all nodes.

Release note: None

[cockroach-teamcity]

This change is 

[ajwerner]

thanks for fixing the test!

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @andrewbaptist)

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pkg/kv/kvserver/client_raft_test.go line 4684 at r2 (raw file):

	// disabled controls whether to disrupt DefaultClass streams.
	var disabled, disabledSystem atomic.Value

one thing that didn't exist when this was written was syncutil.AtomicBool

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pkg/kv/kvserver/client_raft_test.go line 4763 at r2 (raw file):

		// Write to the liveness range on the System class.
		require.NoError(t, db.Put(withTimeout, keyLiveness, 2), "Expected success writing to liveness range")

nit: wrap these long lines

Code quote:

		require.ErrorIs(t, db.Put(withTimeout, keyLiveness, 2), context.DeadlineExceeded, "Expected timeout writing to liveness range")

[andrewbaptist]

pkg/kv/kvserver/client_raft_test.go line 4684 at r2 (raw file):

Previously, ajwerner wrote…

one thing that didn't exist when this was written was syncutil.AtomicBool

Is the primary advantage the removal of the need to cast? Not worth changing for this commit I think

[andrewbaptist]

pkg/kv/kvserver/client_raft_test.go line 4763 at r2 (raw file):

Previously, ajwerner wrote…

nit: wrap these long lines

Done

[andrewbaptist]

bors r=ajwerner

[craig]

Build failed:

• GitHub CI (Cockroach)

[andrewbaptist]

unrelated flake

bors r=ajwerner

[craig]

Build succeeded:

• GitHub CI (Cockroach)