The CI Integration improvement

[lukgni]

Change set:

• add scheduled workflow for chip-tool cross building (build_cr.yaml)
• retrieve last successful run_id from build_cr.yaml using Github REST API
• replace logging using fixed private credentials in run-integration-test-mbed and run-unit-tests scripts (replaced with LAVA_SERVER_USER)
• add script for configuring WLAN AP inside docker container
• update setup_ubuntu_20_04_lts.sh script with new requirements
• add Dockerfile definition for docker image used for testing on RPi (chip-mbed-lava-device/Dockerfile )
• add download_artifacts_by_name_gh() function for downloading specific artifacts (based on its name) from specific run_id