Problem: integration test speed is slow

[leejw51crypto]

currently, same test is done twice.

nix-integration-test: check-network
nix-shell integration_tests/shell.nix --run "pytest -v -n 3 -m 'not ledger' --dist loadscope"
nix-shell integration_tests/shell.nix --run "pytest -v -m ledger"

i suggest separate ledger and non-lendger to different folders,
so ,it makes total integration test faster

[yihuang]

it's separated by marks, "not ledger" and "ledger", they are not overlapped.

[yihuang]

currently ledger tests are running sequentially with other tests, the reason for that is ledger simulator is too costly, slows down the whole github action vm.

[yihuang]

I increased xdist's worker number to 7, the time dropped a bit.
pytest-xdist's scheduling strategy could also have some optimization, currently it treat fast and slow test cases as the same, if we can distribute slow test cases more evenly on workers, we could further shorten the total test running time. pytest-dev/pytest-xdist#255

[tomtau]

it looks like the speed has been a bit improved, but has to be balanced, so that it doesn't timeout on CI -- feel free to reopen this if there's some obvious way for more improvements