Use tox-4 for linters and Molecules

It removes following things:
- skipdist option
- updates whitelist_externals to allowlist_externals
- Drops tox-bindep as it does not support tox-4
- Tox-4 also includes fix for hanging issue:
  https://github.com/tox-dev/tox/issues/2595

bindep is quite stable and tox-4 is around from long
time and tox-bindep last got released on jan 2021. [1]
https://github.com/tox-dev/tox-bindep/releases/tag/0.2.1

So, We are dropping it.

Closes-Bug: #2000622

Signed-off-by: Chandan Kumar <chkumar@redhat.com>
Change-Id: Ia7f8a4dd970ac76322adadc0698ac1c14aa87180

tox.ini

@@ -1,10 +1,6 @@
 [tox]
 minversion = 3.9.0
 envlist = linters
-skipdist = True
-requires =
-    tox<4
-    tox-bindep>=0.2.1
 
 [testenv]
 basepython = python3
@@ -23,7 +19,7 @@ passenv =
     TERM
 deps =
     -r {toxinidir}/test-requirements.txt
-whitelist_externals = bash
+allowlist_externals = bash
 
 [testenv:bindep]
 basepython = python3
@@ -39,7 +35,7 @@ deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/doc/requirements.txt
 basepython = python3
-whitelist_externals = bash
+allowlist_externals = bash
 commands = bash -c ci-scripts/releasenotes_tox.sh
 
 [testenv:linters]