SQL Expressions: Make SQL Expressions work with Alerting (#101820)

Initial support for alerting with SQL expressions

- When `format` is set to `alerting`, SQL expressions output in a format suitable for alerting evaluation.
- Outstanding TODOs:
  - Deduplicate output rows
  - Add more tests
  - Fix broken alerting UI rendering (likely due to shape change to undocumented full-long format)
- Basic usage:
  - SQL must return one numeric column and one or more string columns.
  - Each row may become an alert.
  - The alert fires if the numeric value is non-zero.
  - String columns are treated as labels.

---------

Co-authored-by: Konrad Lalik <konradlalik@gmail.com>
Co-authored-by: Tom Ratcliffe <tom.ratcliffe@grafana.com>
Co-authored-by: Sam Jewell <sam.jewell@grafana.com>

pkg/expr/query.request.schema.json

@@ -942,6 +942,7 @@
             "type": "object",
             "required": [
               "expression",
+              "format",
               "type",
               "refId"
             ],
@@ -976,6 +977,9 @@
                   "SELECT * FROM A LIMIT 1"
                 ]
               },
+              "format": {
+                "type": "string"
+              },
               "hide": {
                 "description": "true if query is disabled (ie should not be returned to the dashboard)\nNOTE: this does not always imply that the query should not be executed since\nthe results from a hidden query may be used as the input to other queries (SSE etc)",
                 "type": "boolean"
@@ -1083,4 +1087,4 @@
   },
   "additionalProperties": false,
   "$schema": "https://json-schema.org/draft-04/schema#"
-}
+}