gh-143253: Add libabigail suppression file for internal types

Changes to internal structs in Include/internal/pycore_*.h cause false
positive ABI violations in make check-abidump because these types are
transitively reachable from public APIs like PyInterpreterState. The
internal struct layout is not part of the public ABI contract.

This adds a suppression specification file that filters out types
defined in pycore_*.h files using a regex pattern, and explicitly
suppresses PyInterpreterState, _PyRuntimeState, and PyThreadState
which are public typedefs aliasing internal structs. The Makefile
is updated to pass the suppression file to abidiff.

Author: pablogsal

Makefile.pre.in

@@ -1883,7 +1883,7 @@ regen-abidump: all
 
 .PHONY: check-abidump
 check-abidump: all
-	abidiff $(srcdir)/Doc/data/python$(LDVERSION).abi "libpython$(LDVERSION).so" --drop-private-types --no-architecture --no-added-syms
+	abidiff $(srcdir)/Doc/data/python$(LDVERSION).abi "libpython$(LDVERSION).so" --drop-private-types --no-architecture --no-added-syms --suppressions $(srcdir)/Misc/libabigail.abignore
 
 .PHONY: regen-limited-abi
 regen-limited-abi: all

Misc/libabigail.abignore

@@ -0,0 +1,21 @@
+# libabigail suppression file for CPython ABI checks
+#
+# Suppress types defined directly in internal headers (pycore_*.h)
+# Regex matches filenames NOT starting with "pycore_", so pycore_* types are suppressed.
+[suppress_type]
+  source_location_not_regexp = ^([^p]|p[^y]|py[^c]|pyc[^o]|pyco[^r]|pycor[^e]|pycore[^_])
+  accessed_through = pointer
+
+# Suppress public typedefs that alias internal structs.
+# These are public names but their underlying struct layout is internal.
+[suppress_type]
+  name = PyInterpreterState
+  accessed_through = pointer
+
+[suppress_type]
+  name = _PyRuntimeState
+  accessed_through = pointer
+
+[suppress_type]
+  name = PyThreadState
+  accessed_through = pointer