CheckRegexString to make sure the string is a valid RE2 expression.

ConvertRegexMatchAndSubstitute into safe variant consumable by envoy.

NewCheckedRegex creates a new regex matcher with the given regex.

NewRegex creates a new regex matcher with the given regex.

NewRegexFromSettings wraps NewRegexWithProgramSize with the program size from the settings.

NewRegexWithProgramSize creates a new regex matcher with the given program size.