[CI/tests] Mark regtest tests instead of skipping them

[merc1er]

The regtest tests were skipped as they require a local node and a Bitcoin.com type REST API to run locally. This decreases code coverage below 90%.

Instead of skipping them, I am flagging them in this PR with a --regtest marker. By default, the regtest tests are not run, but if python run_test.py --regtest or pytest --regtest is used, it will run them using default ports to connect to the local node.

[ghost]

Looking good but we're still a hair below 90%. Any way we can get over that or should we bump the target to 89%?

[merc1er]

OK @teran-mckinney I added a couple more tests to bring coverage to exactly 90% for now 😅

We should probably focus on bringing that number even higher in a later PR.

[ghost]

Nice work!