CI: adjust .ci/common.py users to pmbootstrap ci (MR 3608)

Adjust all CI scripts that make use of .ci/common.py to
'pmbootstrap ci'. Move all scripts that are not direct entry points to
running CI scripts to .ci/lib.

Comment out the dtb check, as it is failing. Apparently it didn't run
properly before. Let's fix this after this CI change is done.

.ci/apkbuild-lint.sh

@@ -0,0 +1,22 @@
+#!/bin/sh -e
+# Description: run apkbuild-lint on modified APKBUILDs
+# Options: native
+# Use 'native' because it requires git commit history.
+# https://postmarktos.org/pmb-ci
+
+if [ "$(id -u)" = 0 ]; then
+	set -x
+	wget "https://gitlab.com/postmarketOS/ci-common/-/raw/master/install_pmbootstrap.sh"
+	sh ./install_pmbootstrap.sh
+	exec su "${TESTUSER:-pmos}" -c "sh -e $0"
+fi
+
+# Wrap pmbootstrap to use this repository for --aports
+pmaports="$(cd $(dirname $0)/..; pwd -P)"
+_pmbootstrap="$(command -v pmbootstrap)"
+pmbootstrap() {
+	"$_pmbootstrap" --aports="$pmaports" "$@"
+}
+
+.ci/lib/apkbuild_linting.py
+