cli: update TestUnavailableZip for partial unavailability

This commit removes the datadriven.RunTest call from
TestUnavailableZip, as this unit test is meant to test the
ability of debug zip to output while nodes are unavailable,
and not meant to assert the entire output is deterministic.

The commit also refactors the test cases to test output for
a cluster with a partially unavailable node and a fully
unavailable node. In the first case, we block replica
requests from the node to table data, simulating SQL
unavailability. In the second case, we block all replica
requests from the node, extending the unavailability to
liveness and status endpoints. To ensure the test doesn't
take too long, we reduce the debug zip timeout from 0.5s
to 0.25s.

Fixes cockroachdb#106961.

Release note: None

Author: Eric Harmeling