Remove cppcheck from CI, add to tools/

We don't enforce cppcheck through the CI, although it's there since
years. It runs on Ubuntu 18/20, so it's old. For folks, it's likely not
discoverable on how to run it locally. Let's make a fresh start.

This removes cppcheck from all CI-related code. Instead, it adds it
under tools/cppcheck/, including documentation on how to run it locally,
bare-matel or in docker.

Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>

tools/cppcheck/run-cppcheck.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# SPDX-License-Identifier: MIT
+
+cppcheck --enable=warning --force \
+    --inline-suppr \
+    --quiet \
+    -i openair1/PHY/CODING/nrLDPC_decoder/nrLDPC_decoder.c \
+    --suppressions-list=tools/cppcheck/suppressions.list \
+    -I common/utils \
+    -I openair3/NAS/COMMON/UTIL \
+    -j`nproc` .