82b6332b91 create a set of recognized denomination forms (yancy)
Pull request description:
I took a stab at restricting the acceptable forms here. There was some consensus that "BtC" was confusing that was discussed in a previous pr https://github.com/rust-bitcoin/rust-bitcoin/pull/1715.
Also, personally I felt that the `PossiblyConfusingDenomination` enum variant was itself confusing. I think it's probably cleaner to just maintain a list of acceptable forms and treat everything else as unknown. For now I just created a const of possibly confusing forms.
ACKs for top commit:
Kixunil:
ACK 82b6332b91
apoelstra:
ACK 82b6332b91
Tree-SHA512: f3c212046e4d8a34ce2d50f34065b1778ae190ca80dd9ad73ef41eb5925705c88c0a764ec149d731eb1735d670c5542415953633a7f3f672d0c1e46b6e004d0b