Add a command to disable all application commands

[karlsbjorn]

Description of the changes

Adds slash disableall which will disable all app commands that are not force-enabled by the cog they come from
Closes #6474

Have the changes in this PR been tested?

Yes

[japandotorg]

just an imo, i'd personally prefer an ux with either of these more instead-

1. running [p]slash disable without any command_name arguments (or an all argument?) disables all slash commands while respecting the command_type argument (i.e., it only disables either slash, message or user [and/or maybe an all literal too?) application commands while sending a "(y/n) warning" stating about this, something like "using this command will disable all slash/message/user application commands, do you wish to continue? (y/n) (and/or with ConfirmView buttons)"
2. a subcommand for [p]slash disable ([p]slash disable all <command_type>), prolly similar to 1. while sending a warning message (with buttons? ConfirmView) and for slash, message or user (and/or maybe an all argument literal for the command_type as well)