github-ci: avoid of use container tags in actions

Changed the following workflows:

  luacheck
  debug_coverage
  release*
  static_build
  static_build_cmake_linux

It was changed the OS in which the test run from debian to ubuntu.
Also changed the way how this OS was booted - before the change it
was booted as docker container using Github Actions tag from inside
the worklfows. And it caused all the workflow steps to be run inside
it. After the change no container run anymore on the running host.
Github Actions host uses for now with its native OS set in 'runs'
tag. It was decided to use the latest one OS `ubuntu-20.04` which is
already the default for 'ubuntu-latest' tag.

This change gave us the abilities to:
 - Remove extra container step in workflow.
 - Switch off swap using 'swapoff' command.
 - Use the same OS as Github Actions uses by default.
 - Setup our local hosts using Github Actions image snapshot.
 - Enable use of actions/checkout@v2.3.4 which is better than v1.
 - Light bootstrap of packages in local .*.mk makefile for:
     build: libreadline-dev libunwind-dev
     tests: pip install -r test-run/requirements.txt

Closes tarantool/tarantool-qa#101