Alpine Linux tests

Add Dockerfile and corresponding tox file to add alpine linux 3.21 & 3.22 to the test suite
Add apk as another package manager in the automated install tests
Use short switches for su command as busybox's su does not accept long switches here
Add Alpine test to github workflow

Signed-off-by: Michael Ziminsky (Z) <mgziminsky@users.noreply.github.com>

test/tox.alpine_3_21.ini

@@ -0,0 +1,10 @@
+[tox]
+envlist = py3
+
+[testenv:py3]
+allowlist_externals = docker
+deps = -rrequirements.txt
+setenv =
+    COLUMNS=120
+commands = docker buildx build --load --progress plain -f _alpine_3_21.Dockerfile -t pytest_pihole:test_container ../
+           pytest {posargs:-vv -n auto} ./test_any_automated_install.py ./test_any_utils.py