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/platform/services/searchengine/interface.go

@@ -47,6 +47,8 @@ type SearchEngineInterface interface {
 	DeleteFilesBatch(rctx request.CTX, endTime, limit int64) *model.AppError
 	TestConfig(rctx request.CTX, cfg *model.Config) *model.AppError
 	PurgeIndexes(rctx request.CTX) *model.AppError
+	PurgeIndexList(rctx request.CTX, indexes []string) *model.AppError
 	RefreshIndexes(rctx request.CTX) *model.AppError
 	DataRetentionDeleteIndexes(rctx request.CTX, cutoff time.Time) *model.AppError
+	IsChannelsIndexVerified() bool
 }