Issue #19655: Replace the ASDL parser carried with CPython

The new parser does not rely on Spark (which is now removed from our repo),
uses modern 3.x idioms and is significantly smaller and simpler.

It generates exactly the same AST files (.h and .c), so in practice no builds
should be affected.

Author: eliben

Misc/NEWS

@@ -57,6 +57,11 @@ Core and Builtins
 
 - Issue #19995: %c, %o, %x, and %X now raise TypeError on non-integer input.
 
+- Issue #19655: The ASDL parser - used by the build process to generate code for
+  managing the Python AST in C - was rewritten. The new parser is self contained
+  and does not require to carry long the spark.py parser-generator library;
+  spark.py was removed from the source base.
+
 - Issue #12546: Allow \x00 to be used as a fill character when using str, int,
   float, and complex __format__ methods.