Automatic channel category sorting (#30866)

* Automatic channel category sorting

* Fix types

* AIed

* Fix issue where categories are updated for all users

* Move all logic to server, clean up

* PR feedback

* Fix lint

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

server/channels/db/migrations/postgres/000138_add_default_category_name_to_channel.down.sql

@@ -0,0 +1 @@
+ALTER TABLE channels DROP COLUMN IF EXISTS DefaultCategoryName; 

server/channels/db/migrations/postgres/000138_add_default_category_name_to_channel.up.sql

@@ -0,0 +1 @@
+ALTER TABLE channels ADD COLUMN IF NOT EXISTS DefaultCategoryName varchar(64) NOT NULL DEFAULT '';