chore: add usage tracking package (#19095)

Not used in coderd yet, see stack.

Adds two new packages:
- `coderd/usage`: provides an interface for the "Collector" as well as a stub implementation for AGPL
- `enterprise/coderd/usage`: provides an interface for the "Publisher" as well as a Tallyman implementation

Relates to https://github.com/coder/internal/issues/814

coderd/apidoc/docs.go

@@ -15701,6 +15701,7 @@ const docTemplate = `{
                 "system",
                 "tailnet_coordinator",
                 "template",
+                "usage_event",
                 "user",
                 "user_secret",
                 "webpush_subscription",
@@ -15742,6 +15743,7 @@ const docTemplate = `{
                 "ResourceSystem",
                 "ResourceTailnetCoordinator",
                 "ResourceTemplate",
+                "ResourceUsageEvent",
                 "ResourceUser",
                 "ResourceUserSecret",
                 "ResourceWebpushSubscription",

coderd/apidoc/swagger.json

@@ -14262,6 +14262,7 @@
 				"system",
 				"tailnet_coordinator",
 				"template",
+				"usage_event",
 				"user",
 				"user_secret",
 				"webpush_subscription",
@@ -14303,6 +14304,7 @@
 				"ResourceSystem",
 				"ResourceTailnetCoordinator",
 				"ResourceTemplate",
+				"ResourceUsageEvent",
 				"ResourceUser",
 				"ResourceUserSecret",
 				"ResourceWebpushSubscription",