Disable selecting enterprise plugins with no license (#28758)

* Add unlicensed property to plugins

* Disable selecting unlicensed plugin

* Add customizable plugin market place url

* License: workaround enabled only in enterprise

* linter

* Move licensing info to front end

* Update pkg/services/licensing/oss.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/services/licensing/oss.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/setting/setting.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/setting/setting.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/api/frontendsettings.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update sample.ini

* Update docs

* Update packages/grafana-runtime/src/config.ts

Co-authored-by: Torkel Ödegaard <torkel@grafana.org>

* Update public/app/features/datasources/state/buildCategories.ts

Co-authored-by: Torkel Ödegaard <torkel@grafana.org>

* Update pkg/api/frontendsettings.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/setting/setting.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Fix spelling

Co-authored-by: Leonard Gram <leo@xlson.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
Co-authored-by: Torkel Ödegaard <torkel@grafana.org>

docs/sources/administration/configuration.md

@@ -1336,6 +1336,10 @@ Set to `true` if you want to test alpha plugins that are not yet ready for gener
 
 Enter a comma-separated list of plugin identifiers to identify plugins that are allowed to be loaded even if they lack a valid signature.
 
+### marketplace_url
+
+Custom install/learn more url for enterprise plugins. Defaults to https://grafana.com/grafana/plugins/.
+
 <hr>
 
 ## [plugin.grafana-image-renderer]