[DOCS] add hints about python re regex syntax instead of PCRE for minion targeting documentation

Description
During my tries to figure out the regex syntax for minion ID / compound targeting as described e.g. in https://docs.saltproject.io/en/latest/topics/targeting/globbing.html#regular-expressions and https://docs.saltproject.io/en/latest/topics/targeting/compound.html#targeting-compound and after asking on Slack it seems the hints present about "PCRE" regexes are slightly misleading. As this also uses the python re syntax ( https://docs.python.org/3/library/re.html ) no character classes / named sets like e.g. [[:alnum:]] are supported.

Suggested Fix
Please add a hint about python re ( https://docs.python.org/3/library/re.html ) implementation regarding the regex syntax everywhere that mentions PCRE where this is applicable. Note: such hints are already present in the documentation of some salt state/execution modules (e.g. https://docs.saltproject.io/en/latest/ref/states/all/salt.states.file.html#salt.states.file.replace ) so my confusion probably came from the mention of PCRE.

Type of documentation
Salt documentation:
Using Salt > Targeting Minions > Compound Targeting > Matching the minion id / Regular Expressions

Location or format of documentation
https://docs.saltproject.io/en/latest/topics/targeting/globbing.html#regular-expressions
https://docs.saltproject.io/en/latest/topics/targeting/compound.html#targeting-compound

Additional context

Start with the regular-expressions section at the globbing URL and the compound-targeting documentation at the compound URL, then search the referenced documentation for mentions of PCRE. Update each applicable hint to identify Python re syntax and verify that both targeting sections clearly explain the supported regex behavior.