Backport github actions to 2.1

With some modifications:
- drop coverage
- drop doxygen
- do not deploy ABI check, only artifacts

abi-check: abi-monitor 1.10 does not support -make -j8 (1.12 supports though)

An error for 1.10 on ci:
https://github.com/azat/libevent/runs/647860649?check_suite_focus=true#step:4:219

(cherry pi

abi-check: abi-monitor 1.10 does not support -make -j8 (1.12 supports though)

An error for 1.10 on ci:
https://github.com/azat/libevent/runs/647860649?check_suite_focus=true#step:4:219

(cherry picked from commit 448a478a98ae7797c1d1a5f1463c02f1b09982f2)

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Add API/ABI checker (using LVC)

v2 (by azat):
- drop package installations
- use local .abi-check over $HOME/abi-check for build dir
- drop regex check, simply use default values (too complex otherw

Add API/ABI checker (using LVC)

v2 (by azat):
- drop package installations
- use local .abi-check over $HOME/abi-check for build dir
- drop regex check, simply use default values (too complex otherwise)
- use sub-shell to avoid cd back
- add missing quotes
- make the style uniq across the whole file (no tabs for indent, copy-paste?)
- drop `set -x`, use `bash -x abi-check.sh` over
- drop EVENT_ABI_CHECK
- use /usr/bin/env bash as shebang
- use `find | xargs` over `cp $(grep -v)`
- adjust markdown syntax in abi-check/README.md
- adjust link to the publicly available documentation

v3 (by azat):
- docker image
- git check-ignore
- make -j8
- allow to change defaults

Refs: #887
(cherry picked from commit 735c891e71dc7de737dc09cdef26683eea394e66)

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