Bitcoind 23 will use the new `getdeploymentinfo` while versions after 19
(but below 23) will use the `UnifiedSoftForks` field instead of the
`SoftForks UnifiedSoftForks` field.
With this PR the taproot gating logic has been tested on bitcoind
versions: 21, 22, and 23. 21 is when the taproot logic was first added.
In this commit, we add a check during normal node construction to see if
the backend node supports Taproot. If it doesn't, then we want to
shutdown and force the user to take note.
To check if the node supports Taproot, we'll first try the normal
getblockchaininfo call. If this works, cool, then we can rely on the
value. If it doesn't, then we'll fall back to the getdeploymentinfo call
which was added in a recent version of bitcoind [1]. Newer versions of
bitcoind might also have this call, and the getblockchaininfo call, but
not actually populate the softforks field [2]. In this case, we'll fall
back, and we also account for the case when the getblockchaininfo RPC is
removed all together.
[1]: https://github.com/bitcoin/bitcoin/pull/23508
[2]: https://github.com/bitcoin/bitcoin/pull/25114Fixes#6773
