feat(coderd): add has_external_agent flag to template_versions and workspace_builds (#19285)

This pull request introduces support for external workspace management, allowing users to register and manage workspaces that are provisioned and managed outside of the Coder.

* Added has_external_agent field to workspace builds and template versions

coderd/database/queries/templates.sql

@@ -72,6 +72,12 @@ WHERE
 		  ELSE true
 	END
 
+	-- Filter by has_external_agent in latest version
+	AND CASE
+		WHEN sqlc.narg('has_external_agent') :: boolean IS NOT NULL THEN
+			tv.has_external_agent = sqlc.narg('has_external_agent') :: boolean
+		ELSE true
+	END
   -- Authorize Filter clause will be injected below in GetAuthorizedTemplates
   -- @authorize_filter
 ORDER BY (t.name, t.id) ASC