One vector for regexes and matchers

[IhateTrains]

• Removed unneeded escaping backslashes in regexes
• Fixed parsing being broken by registerRegex and registerMatcher using separate vectors. They now use one registeredRegexesAndMatchers vector
• StreamOnly versions of registerRegex and registerMatcher
• Purge of "unused" in ParserHelpers

[Idhrendur]

I like where you're gong with this, but I think the modern idiom is to use std::variant and std::visit instead of inheritance: https://www.bfilipek.com/2020/04/variant-virtual-polymorphism.html

Can you put together another PR on a different branch using that method and see how feasible it is?

And maybe split out the cleanup efforts to a new PR so we can just get things merged.

[Idhrendur]

I'm not sure we should give up on this. I'd like more time to compare to how the std::variant version came out.