[clang_cindex] Support pre- and post-Clang 15 cursor kinds

--- cindex.py
+++ cindex.py
@@ -1313,5 +1313,9 @@
 # The translation unit cursor exists primarily to act as the root cursor for
 # traversing the contents of a translation unit.
-CursorKind.TRANSLATION_UNIT = CursorKind(300)
+# DRAKE EDIT BEGIN
+# As of Clang 15, the number assigned here changed from 300 to 350.
+CursorKind.TRANSLATION_UNIT_300 = CursorKind(300)
+CursorKind.TRANSLATION_UNIT_350 = CursorKind(350)
+# DRAKE EDIT END
 
 ###
