Run some network test cases in parallel to speed them up

[teor2345]

Motivation

Some of our network tests are quite slow, and we're running into test timeouts on Windows.

This is unexpected work in sprint 21.

Solution

Run some network tests in parallel to speed them up.

Review

@oxarbitrage can review this PR. It's a low priority.

ZIP-401 and the security tickets should merge before this PR.

Reviewer Checklist

• Existing tests pass

[oxarbitrage]

I think this looks good, there is am overall 10 seconds improve with the addition of some more coverage.

Running affected tests in the current main:

$ cargo test peer_set::initialize::tests::vectors::local_listener
...
     Running unittests (target/debug/deps/zebra_network-04d5f9f7ec7d481e)

running 3 tests
test peer_set::initialize::tests::vectors::local_listener_fixed_port_localhost_addr ... ok
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_localhost_addr ... ok
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_unspecified_addr ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 53 filtered out; finished in 30.09s

Running affected tests with this PR:

$ cargo test peer_set::initialize::tests::vectors::local_listener
...
     Running unittests (target/debug/deps/zebra_network-04d5f9f7ec7d481e)

running 6 tests
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_localhost_addr_v6 ... ok
test peer_set::initialize::tests::vectors::local_listener_fixed_port_localhost_addr_v4 ... ok
test peer_set::initialize::tests::vectors::local_listener_fixed_port_localhost_addr_v6 ... ok
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_localhost_addr_v4 ... ok
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_unspecified_addr_v4 ... ok
test peer_set::initialize::tests::vectors::local_listener_unspecified_port_unspecified_addr_v6 ... ok

test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 53 filtered out; finished in 20.03s