change: adjust tox black stages to install from requirements file

Also remove uneeded config in the command, it is now set in the pyproject.toml
so IDE's and other tooling outside tox picks up the setting.

Author: jmahlik

pyproject.toml

@@ -0,0 +1,2 @@
+[tool.black]
+line-length = 100

requirements/tox/black_requirements.txt

@@ -0,0 +1 @@
+black==24.3.0

tox.ini

@@ -142,19 +142,23 @@ commands =
 
 [testenv:black-format]
 # Used during development (before committing) to format .py files.
+skip_install = true
 setenv =
     LC_ALL=C.UTF-8
     LANG=C.UTF-8
 commands =
-    black -l 100 ./
+    pip install --exists-action=w -r requirements/tox/black_requirements.txt
+    black ./
 
 [testenv:black-check]
 # Used by automated build steps to check that all files are properly formatted.
+skip_install = true
 setenv =
     LC_ALL=C.UTF-8
     LANG=C.UTF-8
 commands =
-    black -l 100 --diff --color --check ./
+    pip install --exists-action=w -r requirements/tox/black_requirements.txt
+    black --diff --color --check ./
 
 [testenv:clean]
 skip_install = true