Resolves #10156.

This implements the following main pieces of functionality:

• Renames key spec "CHANNEL" to be "NOT_KEY", and update the documentation to indicate it's for cluster routing and not for any other key related purpose.
• Add the getchannels-api, so that modules can now define commands that are subject to ACL channel permission checks.
• Add 4 new flags that describe how a module interacts with a command (SUBSCRIBE, PUBLISH, UNSUBSCRIBE, and PATTERN). They are all technically composable, however not sure how a command could both subscribe and unsubscribe from a command at once, but didn't see a reason to add explicit validation there.
• Add two new module apis RM_ChannelAtPosWithFlags and RM_IsChannelsPositionRequest to duplicate the functionality provided by the keys position APIs.
• The RM_ACLCheckChannelPermissions (only released in 7.0 RC1) was changed to take flags rather than a boolean literal.
• The RM_ACLCheckKeyPermissions (only released in 7.0 RC1) was changed to take flags corresponding to keyspecs instead of custom permission flags. These keyspec flags mimic the flags for ACLCheckChannelPermissions.

NOTE: I considered renaming all of the keyReference/keyResult -> argReference/argResult, but decided against and just added a small comment.

To Do:

• doc PR about channel -> not_key flag (Updated documentation for not key redis-doc#1799)