Alerting: Rule backtesting with experimental UI (#115525)

* add function to convert StateTransition to LokiEntry
* add QueryResultBuilder
* update backtesting to produce result similar to historian
* make shouldRecord public
* filter out noop transitions
* add experimental front-end
* add new fields
* move conversion of api model to AlertRule to validation
* add extra labels
* calculate tick timestamp using the same logic as in scheduler
* implement correct logic of calculating first evaluation timestamp
* add uid, group and folder uid they are needed for jitter strategy

* add JitterOffsetInDuration and JitterStrategy.String()

* add config `backtesting_max_evaluations` to [unified_alerting] (not documented for now)

* remove obsolete tests

* elevate permisisons for backtesting endpoint
* move backtesting to separate dir

pkg/tests/api/alerting/test-data/api_backtesting_data.json

@@ -12,6 +12,9 @@
     },
     "condition": "A",
     "no_data_state": "Alerting",
+    "title": "test-rule-backtesting-data",
+    "rule_group": "test-group",
+    "namespace_uid": "test-namespace",
     "data": [
       {
         "refId": "A",
@@ -193,6 +196,9 @@
     },
     "condition": "C",
     "no_data_state": "Alerting",
+    "title": "test-rule-backtesting-data",
+    "rule_group": "test-group",
+    "namespace_uid": "test-namespace",
     "data": [
       {
         "refId": "A",