feature: opcode enum type implemented in a compatible way with current version

[ChrisCho-H]

• Better types for opcodes #1966 mentions that current opcode is type-unsafe. Type safe version is considered as tricky and breaking change as it might function in a bit different way from it does so far(in any versions) and have reverse opcode, too.
• However, as TS numeric Enum compiles with reverse mapping(https://www.typescriptlang.org/docs/handbook/enums.html#reverse-mappings), we can just change OPS to enum, and export OPS and OPS as REVERSE_OPS for reverse opcode.
• IMO It could be good change as it provides type-safe ops and reverse_ops, without changing the way to use this module(no breaking change)
• Also, I deleted OP_PUBKEY and OP_PUBKEYHASH, which are not used in bitcoin anymore

[junderw]

I think this kind of proves the "compatible way" part not being 100% accurate.

If we look at the JS, then yeah. But TypeScript people will have breakage.

[junderw]

This is a great PR though.

I'm thinking of how to push this through.

[junderw]

Not sure how many people are writing script parsers from scratch just pulling in the OPS though...

The use case of "get opcode from arbitrary string" is probably very niche. But still it's a possible breakage.

[junderw]

These two are missing. This is not compatible.

[junderw]

I'll approve and set it for the next major version milestone due to breakages.