[CLD-9186] Remove onboarding tasklist, add preview banner (#31203)

* Remove pricing modal. Adjust everywhere to instead open mattermost.com/pricing. When air gapped, don't show buttons to view plans.

* Fix lint

* Further clean up of unused code. Fixes for linter

* Remove onboarding tasklist for previews, add Cloud previer banner

* Fixes for linter, i18n

* Revert dev lines

* Fix lint

* When below one minute, switch to seconds

* fix linter

* fixes for PR feedback

* useExternalLink for opening pricing modal with enriched params

* Fix i17n

* Fix style, tests

* Update webapp/channels/src/components/announcement_bar/cloud_preview_announcement_bar/index.tsx

Co-authored-by: Guillermo Vayá <guillermo.vaya@mattermost.com>

* Fix linter

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Co-authored-by: Guillermo Vayá <guillermo.vaya@mattermost.com>

server/public/model/cloud.go

@@ -191,6 +191,7 @@ type Subscription struct {
 	CancelAt                *int64   `json:"cancel_at"`
 	WillRenew               string   `json:"will_renew"`
 	SimulatedCurrentTimeMs  *int64   `json:"simulated_current_time_ms"`
+	IsCloudPreview          bool     `json:"is_cloud_preview"`
 }
 
 func (s *Subscription) DaysToExpiration() int64 {