Missing permissions in the `Permissions` constants

[evieDelta]

i noticed there are a couple of permissions which are missing from the permission constants

Specifically

• 1 << _9 Voice stream video
• 1 << 19 View guild insights
• 1 << 31 Use slash commands
• 1 << 32 Request to speak

(the latter 2 are not currently in the official documentation, and the last one was only added within the past week, but being they are launched features i don't think they'll see any sudden changes at this point and are probably safe to add, and the former 2 have been around for awhile and really shouldn't be missing)

and i also noticed that multiple permissions are missing from the combination constants, notably

• PermissionUseExternalEmojis
• PermissionChangeNickname
• PermissionManageNicknames

are completely absent from even PermissionsAll, in addition to the permissions which are missing from the constants

to which, I'd propose

to PermissionsAlltext

• PermissionUseExternalEmojis

to PermissionsAllVoice

• PermissionVoiceStreamVideo
• PermissionVoiceRequestToSpeak

to PermissionsAll

• PermissionChangeNickname
• PermissionManageNicknames
• PermissionViewGuildInsights

to either PermissionsAll or to PermissionsAllText

• PermissionUseSlashCommands

I've got a commit pretty much ready to go for the constants that are just missing so I'll probably submit a PR for that part later ( edit: #906 )

But i wanted to open an issue about it before submitting anything including any kind of change to the PermissionsAll_ combination constants, because while changing them will make them more accurate to their name, any such change is potential for unintended changes in behavior in anything that might use them (it shouldn't break anything since its only adding permissions, but there is still risk a risk it may cause a bot to act unexpectedly from how it would before) so i figured it was necessary for that to have a period of discussion before any changes are PR'ed