Respect Regexp.compile method signature

[ekohl]

As far as I can tell, Regexp.compile has never accepted a third parameter to Regexp.compile until Ruby 3.2. There it actually is a timeout parameter. In older versions it was discarded as an invalid input. It's unclear to me if this parameter ever worked in the first place.

This PR attemps to still make it work as it was originally intended, but it's unclear what the original goal even was. Perhaps it's better to make an incompatible change to drop the third parameter and instead enhance the flags parameter to support N as a value.

[puppetlabs-jenkins]

Can one of the admins verify this patch?

[joshcooper]

I believe Regexp.compile accepted a third argument in Ruby 1.8, but in 1.9 it was changed to always ignore it ruby/ruby@98e6f9a I'm thinking we should do something similar:

if encoding
  Puppet.warn_once(
    'deprecations', 'regsubst_function_encoding',
    _("The regsubst() function's encoding argument has been ignored since Ruby 1.9 and will be removed in a future release")
  )
end

[ekohl]

So something like this?