Improve OSX dev performance

[convenient]

• Quicker installation times by not having ./dev/instances synced to host machine
• Quicker container php execution without xdebug
• Add ability to filter for specific phpunit test case
• update documentation

This has also improved performance on travis which is nice (although was not the main goal, OSX is slower with volumes than linux)

Travis Before

Travis After

Logs

$ time make docker-up docker-install ENV=m23
.....
  real  8m23.443s
  user  0m0.240s
  sys   0m0.259s

$ time make docker-test ENV=m23
docker exec -it uphelper-m23 ./dev/Docker/run-phpunit-functional-tests.sh
PHPUnit 9.6.4 by Sebastian Bergmann and contributors.

Test 'FunctionalTests::testMagentoTwoThree' started
Test 'FunctionalTests::testMagentoTwoThree' ended

Generated command: php /src/bin/patch-helper.php analyse --pad-table-columns 130 --sort-by-type --vendor-namespaces Ampersand --php-strict-errors  /src/dev/instances/magentom23
Test 'FunctionalTests::testMagentoTwoThreeShowCustomModules' started
Test 'FunctionalTests::testMagentoTwoThreeShowCustomModules' ended

Generated command: php /src/bin/patch-helper.php analyse --pad-table-columns 130 --sort-by-type --vendor-namespaces Ampersand,Amazon --php-strict-errors  /src/dev/instances/magentom23
Test 'FunctionalTests::testAutoApplyPatches' started
Test 'FunctionalTests::testAutoApplyPatches' ended

Generated command: php /src/bin/patch-helper.php analyse --auto-theme-update 5 --php-strict-errors  /src/dev/instances/magentom23
Test 'FunctionalTests::testUnifiedDiffIsProvided' started
The patch file could not be parsed, check it's generated with diff -urN
Test 'FunctionalTests::testUnifiedDiffIsProvided' ended

Generated command: php /src/bin/patch-helper.php analyse  --php-strict-errors  /src/dev/instances/magentom23

Time: 05:55.672, Memory: 6.00 MB

OK (4 tests, 19 assertions)

real    5m58.083s
user    0m0.087s
sys 0m0.086s

Checklist

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] Tests have been ran / updated