Enable log line grouping for more logs

[ymyzk]

It's nice to group log lines such as "installdeps" other than "run-test" but this is a bit tricky due to some technical difficulties. Things need to consider:

• Which tox hooks to use: https://tox.readthedocs.io/en/latest/plugins.html#module-tox.hookspecs
• envs are not always created when running tox
• Needs to deal with errors while installing dependencies.

---

Current Behavior

$ tox -e flake8
GLOB sdist-make: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/setup.py
flake8 create: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/flake8
flake8 installdeps: flake8
flake8 inst: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ file:///Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
::group::tox: flake8
flake8 run-test-pre: PYTHONHASHSEED='3474553861'
flake8 run-test: commands[0] | flake8 setup.py
::endgroup::
________________________________________________________________________________________ summary ________________________________________________________________________________________
  flake8: commands succeeded
  congratulations :)

$ tox -e flake8                                                                                                                                                        -? (git)-[master]
GLOB sdist-make: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/setup.py
flake8 inst-nodeps: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ file:///Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
::group::tox: flake8
flake8 run-test-pre: PYTHONHASHSEED='4256965523'
flake8 run-test: commands[0] | flake8 setup.py
::endgroup::
________________________________________________________________________________________ summary ________________________________________________________________________________________
  flake8: commands succeeded
  congratulations :)

Expected Behavior

$ tox -e flake8
GLOB sdist-make: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/setup.py
::group::tox: flake8
flake8 create: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/flake8
flake8 installdeps: flake8
flake8 inst: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ file:///Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 run-test-pre: PYTHONHASHSEED='3474553861'
flake8 run-test: commands[0] | flake8 setup.py
::endgroup::
________________________________________________________________________________________ summary ________________________________________________________________________________________
  flake8: commands succeeded
  congratulations :)

$ tox -e flake8                                                                                                                                                        -? (git)-[master]
GLOB sdist-make: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/setup.py
::group::tox: flake8
flake8 inst-nodeps: /Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 installed: flake8==3.9.2,mccabe==0.6.1,pycodestyle==2.7.0,pyflakes==2.3.1,UNKNOWN @ file:///Users/yusuke/Development/github.com/ymyzk/tox-gh-actions/tox-gh-actions-test/.tox/.tmp/package/1/UNKNOWN-0.0.0.zip
flake8 run-test-pre: PYTHONHASHSEED='4256965523'
flake8 run-test: commands[0] | flake8 setup.py
::endgroup::
________________________________________________________________________________________ summary ________________________________________________________________________________________
  flake8: commands succeeded
  congratulations :)