Tests fail - bitcoin-cli not found.

[lawlawlaw]

I ran the tests with --features bitcoind_22_0. The tests failed due to the following error:

bitcoin-cli not found. Is bitcoin-cli (part of Bitcoin Core) available in your PATH?

As the bitcoind_22_0 feature is enabled, bitcoin-cli should be found.

[RCasatta]

Up until now bitcoind crate rely only on bitcoind executable being in PATH or given through BITCOIND_EXE.

However, core lightning needs more than one executables being in path so this crate this a little work to make it work (other than bitcoin-cli I imagine also lightning-cli lightning-gossip....)