Start log line grouping earlier when possible

[ymyzk]

Description

tox-gh-actions writes ::group::tox: ... earlier if possible using other existing hooks provided by tox.
It shouldn't write the same ::group::tox: ... multiple times.

This PR mitigates the problem described in #39 and #80.

Expected Behavior

Before

py39-macos create: .tox/py39-macos
py39-macos installdeps: flake8
py39-macos inst: .tox/.tmp/package/1/UNKNOWN-0.0.0.zip
py39-macos installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ .tox/.tmp/package/1/UNKNOWN-0.0.0.zip
::group::tox: py39-macos
py39-macos run-test-pre: PYTHONHASHSEED='1271455815'
py39-macos run-test: commands[0] | flake8
::endgroup::

After

py39-macos create: .tox/py39-macos
::group::tox: py39-macos
py39-macos installdeps: flake8
py39-macos inst: .tox/.tmp/package/1/UNKNOWN-0.0.0.zip
py39-macos installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ .tox/.tmp/package/1/UNKNOWN-0.0.0.zip
py39-macos run-test-pre: PYTHONHASHSEED='1271455815'
py39-macos run-test: commands[0] | flake8
::endgroup::

[codecov-commenter]

Codecov Report

Merging #90 (7665569) into master (d7a86ae) will increase coverage by 2.17%.
The diff coverage is 91.30%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
+ Coverage   86.31%   88.49%   +2.17%     
==========================================
  Files           2        2              
  Lines          95      113      +18     
  Branches       25       28       +3     
==========================================
+ Hits           82      100      +18     
+ Misses          6        5       -1     
- Partials        7        8       +1     

Impacted Files	Coverage Δ
src/tox_gh_actions/plugin.py	88.28% <91.30%> (+2.26%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d7a86ae...7665569. Read the comment docs.