fix(GuildManager): add missing toString() on Permission#resolve fns

[Fyko]

Please describe the changes this PR makes and why it should be merged:
This PR adds missing toString functions on various Permissions#resolve(...) functions within GuildManager#create.
This should be treated with high severity.

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

[kyranet]

An alternative to this would have been doing new Permissions() since its toJSON() serializes the data correctly, but this also works.