test_runner: report error on missing sourcemap source

Co-Authored-By: Jayden Seric <me@jaydenseric.com>
Co-Authored-By: Colin Ihrig <cjihrig@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/55037
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/errors.md

@@ -2586,6 +2586,12 @@ disconnected socket.
 
 A call was made and the UDP subsystem was not running.
 
+<a id="ERR_SOURCE_MAP_MISSING_SOURCE"></a>
+
+### `ERR_SOURCE_MAP_MISSING_SOURCE`
+
+A file imported from a source map was not found.
+
 <a id="ERR_SQLITE_ERROR"></a>
 
 ### `ERR_SQLITE_ERROR`