Give moderators access to edit channels (#4608)

Give moderators access to edit channels (#4608)

* give admins access to edit all channels

closes #4598

* test(channels): +admin update another users channel

* Fix tests

* fix(server): delete another users channel

Since the channel owner isn't necessary the auth user we need to check
the right account whether it's the last video or not.

* REMOVE_ANY_VIDEO_CHANNEL > MANAGE_ANY_VIDEO_CHANNEL

Merge REMOVE_ANY_VIDEO_CHANNEL and MANY_VIDEO_CHANNELS to
MANAGE_ANY_VIDEO_CHANNEL.

* user-right: moderator can't manage admins channel

* client: MyVideoChannelCreateComponent > VideoChannelCreateComponent

* client: MyVideoChannelEdit > VideoChannelEdit

* Revert "user-right: moderator can't manage admins channel"

This reverts commit 2c627c154e2bfe6af2e0f45efb27faf4117572f3.

* server: clean dupl validator functionality

* fix ensureUserCanManageChannel usage

It's not async anymore.

* server: merge channel validator middleares

ensureAuthUserOwnsChannelValidator & ensureUserCanManageChannel gets
merged into one middleware.

* client(VideoChannelEdit): redirect to prev route

* fix(VideoChannels): handle anon users

* client: new routes for create/update channel

* Refactor channel validators

Co-authored-by: Chocobozzz <me@florianbigard.com>