chore: Improve efficiency of Docker fixtures in integration_tests

[gruuya]

The goal of this issue would be to improve the following

1. Currently each integration test relies on separate docker containers, meaning there's some time being lost starting/stopping (and building) containers for each test individually.
   • this doesn't seem strictly required, as most or even all present integration tests can be run on the same set of containers
   • moreover, sharing the same set of containers means tests could be run concurrently (they're run sequentially atm)
2. A corollary to 1 is that adding multiple tests which call set_test_fixture into the same file is not reliable as there are docker container port races ongoing
   • this is a problem because it forces people to split tests across different files, increasing compilation (+ docker) time as each file in tests folder is compiled into a separate binary and executed serially: https://corrode.dev/blog/tips-for-faster-rust-compile-times/#combine-all-integration-tests-into-a-single-binary
   • one way to resolve it now is by being explicit that those tests should be executed serially
   • ideally though this is resolved alongside 1, i.e. by sharing docker infra between the tests

Presumably at some point there might be tests that actually change something which other tests shouldn't observe, so the ideal solution would allow for having a separate set of containers for those tests alone, and shared ones for all the rest.

[gruuya]

One proposal for how to resolve this is #924