glapi: fix build dependencies by putting all xml/py files into a single list

This fixes missing script dependencies that didn't trigger rebuilds when
those files were changed. To keep it simple stupid, all xml and python
files used by python scripts indirectly are now in a single global list.

All variables holding file names are also inlined, so that we use file
paths everywhere.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33634>

src/mapi/es2api/meson.build

@@ -3,10 +3,10 @@
 
 es2_glapi_mapi_tmp_h = custom_target(
   'es2_glapi_mapi_tmp.h',
-  input : [glapi_gen_mapi_py, glapi_gen_gl_xml],
+  input : ['../new/gen_gldispatch_mapi.py', '../glapi/registry/gl.xml'],
   output : 'glapi_mapi_tmp.h',
   command : [prog_python, '@INPUT0@', 'glesv2', '@INPUT1@'],
-  depend_files : glapi_gen_mapi_deps,
+  depend_files : glapi_xml_py_deps,
   capture : true,
 )