Add read_channel_content permission (#24118)

* Add read_channel_content permission

* fix tests

* update system console default permissions per role

* add read_channel_content to e2e defaultRolesPermissions

* Migration to include custom roles

* change deprecated isNotExactRole for isNotRole

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/authorization.go

@@ -404,5 +404,5 @@ func (a *App) SessionHasPermissionToManageBot(session model.Session, botUserId s
 }
 
 func (a *App) HasPermissionToReadChannel(c request.CTX, userID string, channel *model.Channel) bool {
-	return a.HasPermissionToChannel(c, userID, channel.Id, model.PermissionReadChannel) || (channel.Type == model.ChannelTypeOpen && a.HasPermissionToTeam(userID, channel.TeamId, model.PermissionReadPublicChannel))
+	return a.HasPermissionToChannel(c, userID, channel.Id, model.PermissionReadChannelContent) || (channel.Type == model.ChannelTypeOpen && a.HasPermissionToTeam(userID, channel.TeamId, model.PermissionReadPublicChannel))
 }