Alerting: Update rule API to address folders by UID (#74600)

* Change ruler API to expect the folder UID as namespace

* Update example requests

* Fix tests

* Update swagger

* Modify FIle field in /api/prometheus/grafana/api/v1/rules

* Fix ruler export

* Modify folder in responses to be formatted as <parent UID>/<title>

* Add alerting test with nested folders

* Apply suggestion from code review

* Alerting: use folder UID instead of title in rule API (#77166)

Co-authored-by: Sonia Aguilar <soniaaguilarpeiron@gmail.com>

* Drop a few more latent uses of namespace_id

* move getNamespaceKey to models package

* switch GetAlertRulesForScheduling to use folder table

* update GetAlertRulesForScheduling to return folder titles in format `parent_uid/title`.

* fi tests

* add tests for GetAlertRulesForScheduling when parent uid

* fix integration tests after merge

* fix test after merge

* change format of the namespace to JSON array

this is needed for forward compatibility, when we migrate to full paths

* update EF code to decode nested folder

---------

Co-authored-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>
Co-authored-by: Virginia Cepeda <virginia.cepeda@grafana.com>
Co-authored-by: Sonia Aguilar <soniaaguilarpeiron@gmail.com>
Co-authored-by: Alex Weaver <weaver.alex.d@gmail.com>
Co-authored-by: Gilles De Mey <gilles.de.mey@gmail.com>

pkg/services/ngalert/api/test-data/ruler-grafana-recipient.http

@@ -1,7 +1,7 @@
 @grafanaRecipient = grafana
 
-// should point to an existing folder named alerting
-@namespace1 = foo%20bar
+// should point to an existing folder UID
+@namespace1 = baf2c548-5e1e-42e8-8fde-8320e50d801e
 
 // create group42 under unknown namespace - it should fail
 POST http://admin:admin@localhost:3000/api/ruler/{{grafanaRecipient}}/api/v1/rules/unknown