Alerting: Refactor API types generation with different names. (#51785)

This changes the API codegen template (controller-api.mustache) to simplify some names. When this package was created, most APIs "forked" to either a Grafana backend implementation or a "Lotex" remote implementation. As we have added APIs it's no longer the case. Provisioning, configuration, and testing APIs do not fork, and we are likely to add additional APIs that don't fork.

This change replaces {{classname}}ForkingService with {{classname}} for interface names, and names the concrete implementation {{classname}}Handler. It changes the implied implementation of a route handler from fork{{nickname}} to handle{{nickname}}. So PrometheusApiForkingService becomes PrometheusApi, ForkedPrometheusApi becomes PrometheusApiHandler and forkRouteGetGrafanaAlertStatuses becomes handleRouteGetGrafanaAlertStatuses

It also renames some files - APIs that do no forking go from forked_{{name}}.go to {{name}}.go and APIs that still fork go from forked_{{name}}.go to forking_{{name}}.go to capture the idea that those files a "doing forking" rather than "are a fork of something."

Signed-off-by: Joe Blubaugh <joe.blubaugh@grafana.com>

pkg/services/ngalert/api/tooling/api.json

@@ -2702,6 +2702,7 @@
    "type": "object"
   },
   "URL": {
+   "description": "The general form represented is:\n\n[scheme:][//[userinfo@]host][/]path[?query][#fragment]\n\nURLs that do not start with a slash after the scheme are interpreted as:\n\nscheme:opaque[?query][#fragment]\n\nNote that the Path field is stored in decoded form: /%47%6f%2f becomes /Go/.\nA consequence is that it is impossible to tell which slashes in the Path were\nslashes in the raw URL and which were %2f. This distinction is rarely important,\nbut when it is, the code should use RawPath, an optional field which only gets\nset if the default encoding is different from Path.\n\nURL's String method uses the EscapedPath method to obtain the path. See the\nEscapedPath method for more details.",
    "properties": {
     "ForceQuery": {
      "type": "boolean"
@@ -2734,7 +2735,7 @@
      "$ref": "#/definitions/Userinfo"
     }
    },
-   "title": "URL is a custom URL type that allows validation at configuration load time.",
+   "title": "A URL represents a parsed URL (technically, a URI reference).",
    "type": "object"
   },
   "Userinfo": {
@@ -3295,6 +3296,7 @@
    "type": "object"
   },
   "receiver": {
+   "description": "Receiver receiver",
    "properties": {
     "name": {
      "description": "name",