avoid using pkg_resources

This is deprecated in python 3.12.
Also, improve file handling

pio-scripts/auto_firmware_version.py

@@ -3,33 +3,27 @@
 # Copyright (C) 2022 Thomas Basler and others
 #
 import os
-import pkg_resources
 
 Import("env")
 
-required_pkgs = {'dulwich'}
-installed_pkgs = {pkg.key for pkg in pkg_resources.working_set}
-missing_pkgs = required_pkgs - installed_pkgs
-
-if missing_pkgs:
+try:
+    from dulwich import porcelain
+except ModuleNotFoundError:
     env.Execute('"$PYTHONEXE" -m pip install dulwich')
-
-from dulwich import porcelain
+    from dulwich import porcelain
 
 
 def updateFileIfChanged(filename, content):
     mustUpdate = True
     try:
-        fp = open(filename, "rb")
+        with open(filename, "rb") as fp:
             if fp.read() == content:
                 mustUpdate = False
-        fp.close()
     except:
         pass
     if mustUpdate:
-        fp = open(filename, "wb")
+        with open(filename, "wb") as fp:
             fp.write(content)
-        fp.close()
     return mustUpdate