Remove (or integrate to CI/pyperformance) Module/_decimal/tests

[skirpichev]

This is a follow-up of #115119.

The bench.py script already partially integrated to the pyperformance, see python/pyperformance#473.

The Modules/_decimal/tests/deccheck.py currently is broken. Even with the patch

diff --git a/Modules/_decimal/tests/deccheck.py b/Modules/_decimal/tests/deccheck.py
index bf277dd6879..b276700bc01 100644
--- a/Modules/_decimal/tests/deccheck.py
+++ b/Modules/_decimal/tests/deccheck.py
@@ -53,6 +53,8 @@
 from formathelper import rand_format, rand_locale
 from _pydecimal import _dec_from_triple
 
+sys.set_int_max_str_digits(0)
+
 C = import_fresh_module('decimal', fresh=['_decimal'])
 P = import_fresh_module('decimal', blocked=['_decimal'])
 EXIT_STATUS = 0

I still got

$ ./python Modules/_decimal/tests/deccheck.py --short


Random seed: 1778644369


testing __abs__ ...
    prec: 3  emin: -3  emax: 3
[...]
testing __hash__ ...
    prec: 3  emin: -3  emax: 3
Traceback (most recent call last):
  [...]
  File "/home/sk/src/cpython/Modules/_decimal/tests/deccheck.py", line 570, in skip_error
    return getattr(shandler, t.funcname, shandler.default)(t)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
TypeError: 'NoneType' object is not callable

Probably these tests now are partially overlap with the CI tests. I think we should investigate this and merge tests or just run deccheck.py as part of CPython test suite.