Add a source post hook (#1059)

Add a post hook to `source` to automatically reload `gef` commands and move `@register`-ed new commands to being active.

gef.py

@@ -11484,5 +11484,9 @@ def target_remote_posthook():
 
     # restore saved breakpoints (if any)
     bkp_fpath = pathlib.Path(gef.config["gef.autosave_breakpoints_file"]).expanduser().absolute()
-    if bkp_fpath.exists() and bkp_fpath.is_file():
+    if bkp_fpath.is_file():
         gdb.execute(f"source {bkp_fpath}")
+
+    # Add a `source` post hook to force gef to recheck the registered plugins and
+    # eventually load the missing one(s)
+    gdb.execute("define hookpost-source\npi gef.gdb.load()\nend")