feat: filter users by github user id in the users list CLI command (#17029)

Add the `--github-user-id` option to `coder users list`, which makes the
command only return users with a matching GitHub user id. This will
enable https://github.com/coder/start-workspace-action to find a Coder
user that corresponds to a GitHub user requesting to start a workspace.

docs/reference/cli/users_list.md

@@ -13,6 +13,14 @@ coder users list [flags]
 
 ## Options
 
+### --github-user-id
+
+|      |                  |
+|------|------------------|
+| Type | <code>int</code> |
+
+Filter users by their GitHub user ID.
+
 ### -c, --column
 
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