66d5800ac0 psbt: Add IndexOutOfBounds error (Tobin C. Harding)
Pull request description:
We currently have a bunch of functions that are infallible if the `index` argument is within-bounds however we return a `SignError`, this obfuscates the code.
Add an `IndexOutOfBoundsError`. While we are at it make it an enum so users can differentiate between which vector the out of bounds access was attempted against.
ACKs for top commit:
sanket1729:
utACK 66d5800ac0. This is a clean improvement over existing code.
apoelstra:
ACK 66d5800ac0
Tree-SHA512: fa8a24990d1dcdab0c9b019fb2387b5a518b02d0a65715f0ab62519894b19c0c74750d3dcdc928626fa68b146038b907d79de3ba9712c9287db8fa64693ebc11