Store capability values from CAP v3.2 handshakes + honor SASL v3.2 mechanism lists

[progval]

1. Store capability values in 'CAP LS 302' negotiations.

   So it can be retrieved later (eg. to know what SASL mechanisms are available).

   https://ircv3.net/specs/extensions/capability-negotiation.html#the-cap-ls-subcommand

2. Honor SASL v3.2 mechanism lists

   From https://ircv3.net/specs/extensions/sasl-3.2#usage:

   Clients SHOULD pick a mechanism present in the CAP LS reply they get from the server and attempt to use that mechanism for authentication after they request the sasl capability.

Tested on The Lounge.

[ItsOnlyBinary]

As this is tracking available caps it seems it would be also wise for it to track cap-notify (CAP NEW|DEL) events to keep the list accurate

https://github.com/kiwiirc/irc-framework/blob/cae2d67eb9d4814123da78733ba05891b49ba597/src/commands/handlers/registration.js#L236

https://github.com/kiwiirc/irc-framework/blob/cae2d67eb9d4814123da78733ba05891b49ba597/src/commands/handlers/registration.js#L253

[progval]

Done (but not tested)

[ItsOnlyBinary]

forcing checks to re-run

[ItsOnlyBinary]

:) thanks