scripts: Renamed tracebd.py -> dbgtrace.py

This matches dbgbmap.py and fits in with the other dbg scripts.

The choice of tracebd.py for the name was arbitrary anyways, we just
needed something that wouldn't conflict with other scripts.

scripts/dbgtrace.py

@@ -3,7 +3,7 @@
 # Render operations on block devices based on trace output
 #
 # Example:
-# ./scripts/tracebd.py trace
+# ./scripts/dbgtrace.py trace
 #
 # Copyright (c) 2022, The littlefs authors.
 # SPDX-License-Identifier: BSD-3-Clause