SRI Integration Test Framework: bitcoind

[plebhash]

The second stage of #1120

Requirements:

• Ability to launch a Template Provider (TP) process (SV2-enabled bitcoind in regtest mode) via the bitcoind crate within the new SRI Integration Tests framework described in x.
• SRI requires that the blockchain has at least 16 blocks, so the creation of those should be automated and abstracted away from the framework user (so it doesn’t have to be done explicitly for every test).

This should be useful for tests where orchestrating a bitcoind process in regtest mode is sufficient.

There might be instances however where this is not sufficient. For example, we might want to assert some role’s behavior against an invalid template, which would be rather difficult to generate by simply orchestrating a bitcoind process without access to its internal C++ APIs.

For scenarios where this approach is not sufficient, a TP mock will be required (mocks are detailed #1122).

[plebhash]

@jbesraa should we aim to do this together with #1066 or separate PRs?

[Shourya742]

@plebhash Once the #1066 branch is fixed, I can push my changes as a PR to it.