CloudMigrations: Query Grafana Migration Status for status while the snapshot is in the cloud (#90314)

* implement querying gms for snapshot status

* add some documentation

* provide snapshot resources after snapshot is created

* add rate limiting to backend

* fix compilation error

* fix typo

* add unit tests

* finish merge

* lint

* swagger gen

* more testing

* remove duplicate test

* address a couple PR comments

* update switch statement to a map

* add timeouts to gms client through the http client

* remove extra whitespace

* put method back where it was so the PR is less confusing

* fix tests

* add todo

* fix final unit test

conf/sample.ini

@@ -1858,3 +1858,28 @@ timeout = 30s
 [public_dashboards]
 # Set to false to disable public dashboards
 ;enabled = true
+
+###################################### Cloud Migration ######################################
+[cloud_migration]
+# Set to true to enable target-side migration UI
+;is_target = false
+# Token used to send requests to grafana com
+;gcom_api_token = ""
+# How long to wait for a request sent to gms to start a snapshot to complete
+;start_snapshot_timeout = 5s
+# How long to wait for a request sent to gms to validate a key to complete
+;validate_key_timeout = 5s
+# How long to wait for a request sent to gms to get a snapshot status to complete
+;get_snapshot_status_timeout = 5s
+# How long to wait for a request to fetch an instance to complete
+;fetch_instance_timeout = 5s
+# How long to wait for a request to create an access policy to complete
+;create_access_policy_timeout = 5s
+# How long to wait for a request to create to fetch an access policy to complete
+;fetch_access_policy_timeout = 5s
+# How long to wait for a request to create to delete an access policy to complete
+;delete_access_policy_timeout = 5s
+# The domain name used to access cms
+;domain = grafana-dev.net
+# Folder used to store snapshot files. Defaults to the home dir
+;snapshot_folder = ""