It doesn't work since 2023-11-18. The uploading succeeds, but the
website says:

> The Coverity Build tool version is no longer supported. Please
> download the latest version for your platform from
> https://scan.coverity.com/download...

It seems, some specific toolset is installed in the
`tarantool/testing:debian-buster` image and it was deprecated 11 months
ago.

Recently the CI workflow starts to fail due to use of the old image with
an old CMake in it:

> [  2%] Performing configure step for 'bundled-nanoarrow-project'
> -- Building using CMake version: 3.13.4
> -- Configuring incomplete, errors occurred!
> CMake Error at CMakeLists.txt:19 (cmake_minimum_required):
>   CMake 3.14 or higher is required.  You are running version 3.13.4

It is likely due to commit 49c160c28c97 ("third_party: initial import of
nanoarrow").

Here I refine the workflow file:

* Get rid of the custom docker image with preinstalled Coverity toolset.
* Use a nice unofficial-coverity-scan GitHub Action ([1]).
* Add the `libreadline-dev` dependency installation, because it is
  needed to build tarantool on Ubuntu 24.04.
* Drop related `.test.mk` rules, because it looks more readable to
  invoke a few commands from the workflow file directly.
* Drop testing artifacts uploading that seems a copy-paste from some
  workflow that runs the tests and the given directory unlikely has any
  file in our case.
* Drop unused step that adds a comment to the pull request.

And things seems to start working. At least, after a testing run of the
workflow now I see the following status on the website:

> Last Build Status: Running. Your build is currently being analyzed

[1]: https://github.com/marketplace/actions/unofficial-coverity-scan

See also #10651.

NO_DOC=developer tools
NO_CHANGELOG=see NO_DOC
NO_TEST=see NO_DOC

(cherry picked from commit f5daacfac84fbea3bb67991fa71ea4e789184ec8)