Make RZ_REGEX_EXTENDED behave exactly like PCRE2 documents.

[Rot127]

Is your feature request related to a problem? Please describe.

Make Rizin regex API behave exactly like PCRE2, except documented exceptions.
This is not necessarily a bug but a general problem.

Our regex legacy engine interpreted spaces when the EXTENDED flag was set. PCRE2 doesn't. It just ignores them (literal spaces, \s is still interpreted as blank character).
To not break everything (and fixing all the regex in code) the spaces are replaced with '\s' curretly.

Describe the solution you'd like

Make RZ_REGEX_EXTENDED behave like PCRE2 documentation, so people can refer to the PCRE2 documentation.

Describe alternatives you've considered

Leave it like this and add warnings somewhere.

Additional context

https://github.com/rizinorg/rizin/blob/dev/librz/util/regex.c#L60-L67