This introduces the ability to split asm strings into tokens and assign a type to them.
This means:
* Each asm strings is assigned a list of tokens. Each token points to a sub-string.
* A token has a type attached which describes it (e.g. register token, operator token, mnemonic token etc.)
* A generic parsing method is introduced which splits an asm string into tokens. The pattern it parses is `<mnem> <op> <op> ...`.
* Instead of the generic method, plugins can create the token strings on their own.
* An API method was introduced to help plugins implement their own parsing methods via regex patterns.
* Custom token strings are stored in `RzAsmOp.asm_toks`
Additionally the coloring of asm strings is now exclusively done via the token strings.
* For this a function was added to colorize tokenized asm strings according to their token types.
