MM-67684 Separate shared channel permissions from secure connection permissions (#35409)

* Channel sharing operations (invite, uninvite, list shared channel remotes)
now require ManageSharedChannels instead of ManageSecureConnections, allowing
customers to delegate channel sharing without granting full connection management access.
Endpoints serving both roles (getRemoteClusters, getSharedChannelRemotesByRemoteCluster) accept either permission.

Also adds RequirePermission helpers on Context to reduce boilerplate across all remote cluster and shared channel handlers, and fixes a bug where invite/uninvite checked ManageSecureConnections but reported ManageSharedChannels in the error.

api/v4/source/remoteclusters.yaml

@@ -7,7 +7,7 @@
         Get a list of remote clusters.
 
         ##### Permissions
-        `manage_secure_connections`
+        `manage_secure_connections` or `manage_shared_channels`
       operationId: GetRemoteClusters
       parameters:
         - name: page
@@ -134,7 +134,7 @@
         Get the Remote Cluster details from the provided id string.
 
         ##### Permissions
-        `manage_secure_connections`
+        `manage_secure_connections` or `manage_shared_channels`
       operationId: GetRemoteCluster
       parameters:
         - name: remote_id

api/v4/source/sharedchannels.yaml

@@ -56,7 +56,7 @@
         and their status.
 
         ##### Permissions
-        `manage_secure_connections`
+        `manage_secure_connections` or `manage_shared_channels`
       operationId: GetSharedChannelRemotesByRemoteCluster
       parameters:
         - name: remote_id