Use deterministic randomness in the p2p tests

[stanislav-tkach]

The p2p tests should use deterministic randomness similar to the chainstate tests. Ideally the chainstate test framework can be reused, see #182 for more details.

[stanislav-tkach]

This is partially fixed with https://github.com/mintlayer/mintlayer-core/pull/720, but there are more tests that would benefit from randomness. Unfortunately, it isn't easy to fix because these tests use the libtest-mimic library and it isn't trivial to combine it with rstest.