feat(coderd/database): track user status changes over time (#16019)

RE: https://github.com/coder/coder/issues/15740,
https://github.com/coder/coder/issues/15297

In order to add a graph to the coder frontend to show user status over
time as an indicator of license usage, this PR adds the following:

* a new `api.insightsUserStatusCountsOverTime` endpoint to the API
* which calls a new `GetUserStatusCountsOverTime` query from postgres
* which relies on two new tables `user_status_changes` and
`user_deleted`
* which are populated by a new trigger and function that tracks updates
to the users table

The chart itself will be added in a subsequent PR

---------

Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>

docs/reference/api/schemas.md

@@ -3000,6 +3000,34 @@ Git clone makes use of this by parsing the URL from: 'Username for "https://gith
 |-------|--------|----------|--------------|-------------|
 | `key` | string | false    |              |             |
 
+## codersdk.GetUserStatusCountsResponse
+
+```json
+{
+  "status_counts": {
+    "property1": [
+      {
+        "count": 10,
+        "date": "2019-08-24T14:15:22Z"
+      }
+    ],
+    "property2": [
+      {
+        "count": 10,
+        "date": "2019-08-24T14:15:22Z"
+      }
+    ]
+  }
+}
+```
+
+### Properties
+
+| Name               | Type                                                                      | Required | Restrictions | Description |
+|--------------------|---------------------------------------------------------------------------|----------|--------------|-------------|
+| `status_counts`    | object                                                                    | false    |              |             |
+| » `[any property]` | array of [codersdk.UserStatusChangeCount](#codersdkuserstatuschangecount) | false    |              |             |
+
 ## codersdk.GetUsersResponse
 
 ```json
@@ -6724,6 +6752,22 @@ If the schedule is empty, the user will be updated to use the default schedule.|
 | `dormant`   |
 | `suspended` |
 
+## codersdk.UserStatusChangeCount
+
+```json
+{
+  "count": 10,
+  "date": "2019-08-24T14:15:22Z"
+}
+```
+
+### Properties
+
+| Name    | Type    | Required | Restrictions | Description |
+|---------|---------|----------|--------------|-------------|
+| `count` | integer | false    |              |             |
+| `date`  | string  | false    |              |             |
+
 ## codersdk.ValidateUserPasswordRequest
 
 ```json