Add a Valgrind builder + factory with a selected set of tests

[pablogsal]

No description provided.

[pablogsal]

This bad boy detected the problem in python/cpython#123821:

==602795== Conditional jump or move depends on uninitialised value(s)
==602795==    at 0x240052: tok_get_fstring_mode (tokenizer.c:2705)
==602795==    by 0x241214: tok_get (tokenizer.c:2857)
==602795==    by 0x241214: _PyTokenizer_Get (tokenizer.c:2862)
==602795==    by 0x209857: _PyPegen_fill_token (pegen.c:298)
==602795==    by 0x2245F7: fstring_replacement_field_rule (parser.c:15914)
==602795==    by 0x224FB1: fstring_middle_rule (parser.c:15858)
==602795==    by 0x224FB1: _loop0_114_rule (parser.c:32096)
==602795==    by 0x224FB1: fstring_rule (parser.c:16193)
==602795==    by 0x224FB1: _tmp_259_rule (parser.c:40681)
==602795==    by 0x224FB1: _loop1_115_rule (parser.c:32163)
==602795==    by 0x224FB1: strings_rule (parser.c:16294)
==602795==    by 0x21478F: atom_rule (parser.c:14690)
==602795==    by 0x215D57: primary_raw (parser.c:14328)
==602795==    by 0x215D57: primary_rule (parser.c:14126)
==602795==    by 0x216017: await_primary_rule (parser.c:14080)
==602795==    by 0x216341: power_rule (parser.c:13956)
==602795==    by 0x216341: factor_rule (parser.c:13906)
==602795==    by 0x2169CD: term_raw (parser.c:13747)
==602795==    by 0x2169CD: term_rule (parser.c:13509)
==602795==    by 0x216D2E: sum_raw (parser.c:13463)
==602795==    by 0x216D2E: sum_rule (parser.c:13342)
==602795==    by 0x2170CE: shift_expr_raw (parser.c:13302)
==602795==    by 0x2170CE: shift_expr_rule (parser.c:13181)
==602795==  Uninitialised value was created by a heap allocation
==602795==    at 0x48447A8: malloc (vg_replace_malloc.c:446)
==602795==    by 0x23AD1D: tok_new (tokenizer.c:68)
==602795==    by 0x2410B8: _PyTokenizer_FromFile (tokenizer.c:959)
==602795==    by 0x20AB6C: _PyPegen_run_parser_from_file_pointer (pegen.c:972)
==602795==    by 0x40737C: pyrun_file (pythonrun.c:1634)
==602795==    by 0x40737C: _PyRun_SimpleFileObject (pythonrun.c:433)
==602795==    by 0x4079CB: _PyRun_AnyFileObject (pythonrun.c:78)
==602795==    by 0x4313AB: pymain_run_file_obj (main.c:360)
==602795==    by 0x4313AB: pymain_run_file (main.c:379)
==602795==    by 0x4313AB: pymain_run_python.constprop.0 (main.c:633)
==602795==    by 0x431A2A: Py_RunMain (main.c:713)
==602795==    by 0x431A2A: pymain_main (main.c:743)
==602795==    by 0x431A2A: Py_BytesMain (main.c:767)
==602795==    by 0x49A3E07: (below main) (libc_start_call_main.h:58)

[pablogsal]

I am starting with this and grow slowly the list of tests as we did with the undefined behaviour sanitizer, which proved to be a very successful strategy

[vstinner]

The change LGTM, but I don't know if the buildbot is working :-)