2b0fcff7f2 Make VerifyWitnessProgram use a Span stack (Pieter Wuille)
Pull request description:
Here is a follow-up to #18002, again with the goal of simplifying (potential) BIP341 code.
Instead of passing a begin and end iterator of the initial stack to `ExecuteWitnessScript`, they are turned into a `Span<const valtype>`, representing a span of `valtype`s in memory. This allows `VerifyWitnessProgram` to operate on that span directly, instead of juggling iterators around (which would be exacerbated by #17977 if trying to avoid copying the stack).
ACKs for top commit:
ajtowns:
ACK 2b0fcff7f2
elichai:
ReACK on the diff 2b0fcff7f2
instagibbs:
re-ACK 2b0fcff7f2
theStack:
re-ACK 2b0fcff7f2
Empact:
ACK 2b0fcff7f2
jnewbery:
utACK 2b0fcff7f2
Tree-SHA512: 38eb4ce17f1947674c1c274caa40feb6ea8266bd96134d9cf1bc41e6fbf1114d4dde6c7a9e26e1ca8f3d0155429ef0911cc8ec0c1037d8fe7d6ec7f9e7184e93
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