Memoize regexps for common character classes

[ianks]

This PR improves the performance of Addressable::URI#encode and Addressable::URI#encode_component by memoizing the default character class regexes instead of recompiling them on every call. This results in the following performance improvements:

Addressable::URI#encode_component

Addressable::URI#encode_component (old)
                         95.417k (± 1.4%) i/s -    484.347k in   5.077072s

Addressable::URI#encode_component (new)
                        426.794k (± 1.6%) i/s -      2.134M in   5.001961s

Addressable::URI#encode benchmark

Addressable::URI#encode (old)
                         20.800k (± 1.2%) i/s -    105.213k in   5.058973s

Addressable::URI#encode (new)
                         34.344k (± 2.3%) i/s -    174.794k in   5.092458s

[dentarg]

Nice

[ianks]

@dentarg is there any plan to release main soon-ish? deciding whether we should use github dep in our gemfile or just wait it out

[dentarg]

@ianks No plan, I forgot about this change actually. I can do a release. If someone would open a PR like #505 it would help!

[dentarg]

(note that there's a rake task to update the gemspec (I have my instructions for doing a release at https://starkast.wiki/addressable))

[dentarg]

@ianks 2.8.6 has been released now