qa: Tapscript-Miniscript unit tests

Adapt the test data and the parsing context to support x-only keys.
Adapt the Test() helper to test existing cases under both Tapscript and
P2WSH context, asserting what needs to be valid or not in each.
Finally, add more cases that exercise the logic that was added in the
previous commits (multi_a, different resource checks and keys
serialization under Tapscript, different properties for 'd:' fragment,
..).

Author: darosior