Test suite needs a --skip-long flag or env variable

[pinheadmz]

The coinselection tests are great but take a long time. Also, the taproot test vectors from bitcoin core are like 15 MB. I think we should modify the npm run test script to skip those tests unless flagged manually by the user, and then of course on CI they will always run. The taproot test vector can be hosted in a separate repo and can be cloned locally by the test itself

[theanmolsharma]

Fixed in #1096

To run integration tests locally, you need to run export BCOIN_RUN_LONG_TESTS=true before running the tests.