Add the --override-abi option

[pvdrz]

This option can be used from the CLI with the : syntax and it overrides the ABI of a function if it matches .

Fixes #2257 as the ".*" regex can be used to match every function.

[emilio]

r=me with that simplification.

[pvdrz]

@emilio before we move forward with this, we have this question in #2328 where eventually people would like to have another option with the shape <extra_arg><separator><regex>. Maybe we should agree on the separator before moving forward? I used : here but for the other use of this : won't work because <extra_arg> contains :.

Another suggested option is / but I don't know if that's clear enough

[hcldan]

@pvdrz The option doc was not updated with the new = char change you made.
Also I think you have the abi=regex backwards in the doc. Is it not regex=abi based on the examples in the tests?

[hcldan]

Looks like this got caught in another PR. Nevermind.

[pvdrz]

@hcldan thanks for checking this up! I'm trying to keep those changes in a single PR to avoid this confusion in the future :)