feat(Guild): setChannelPositions parent, lockPermissions keys

[almostSouji]

Please describe the changes this PR makes and why it should be merged:

• Guild#setChannelPositions takes the options parent and lockPermissions as per chore: document missing properties in Modify Channel Positions endpoint discord/discord-api-docs#1776
• This makes the position key optional, however is still only a patch level PR, since the old approach (position being mandatory) can still be used, making this non-breaking.
• c732669 adds CategoryChannelResolvable for this PR only, Use CategoryChannelResolvable for parent setting #5521 to keep track of and apply the type to the rest of the library

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating
• This PR changes the library's interface (methods or parameters added)