Rebuild channel index (#26080)

* WIP

* Added rebuild channels index functionality

* Added rough logic to send message to all sysadmins

* WIP

* WIP

* WIP

* Cleanup

* i18n fix

* reading through all pages of system admins

* Fixed webapp style

* i18n fix

* Added help text

* i18n fix

* i18n update

* Updated system console button action

* Updated snapshots

* some cleanup

* Updated snapshot

* Update server/channels/app/server.go

Co-authored-by: Daniel Espino García <larkox@gmail.com>

* fixed typo

* Refactoring to improve readibility

* moved index check to API later during config update

* Added some docs

* Updated get system bot

---------

Co-authored-by: Daniel Espino García <larkox@gmail.com>

server/public/model/job.go

@@ -12,7 +12,6 @@ const (
 	JobTypeMessageExport                = "message_export"
 	JobTypeElasticsearchPostIndexing    = "elasticsearch_post_indexing"
 	JobTypeElasticsearchPostAggregation = "elasticsearch_post_aggregation"
-	JobTypeElasticsearchFixChannelIndex = "elasticsearch_fix_channel_index"
 	JobTypeBlevePostIndexing            = "bleve_post_indexing"
 	JobTypeLdapSync                     = "ldap_sync"
 	JobTypeMigrations                   = "migrations"