More efficient/reliable testing in CI

[wileyj]

#3763

This is being evaluated in a personal fork https://github.com/wileyj/stacks-blockchain/tree/master but so far the proposal in the issue is showing potential in poc tests.

Other non-testing specific changes are being added and tested to improve the overall experience in building as well.

[wileyj]

closing as this has been merged

[blockstack-devops]

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