Split test suite into independent jobs

[norberttech]

Currently, we run the test suite workflow as a whole in a matrix where we check against:

• 3 PHP versions
• locked/minimum/maximum dependencies

Would be nice to create a job for each component so tests can be executed like this:

composer test:core
composer test:lib:parquet
composer test:adapter:csv

It can be achieved by creating dedicated test suites in phpunit.xml.dist file.

So for example composer test:core under the hood should execute 2 test suites (or more if needed)

./tools/phpunit/vendor/bin/phpunit --testsuite=core-unit
./tools/phpunit/vendor/bin/phpunit --testsuite=core-integration
./tools/phpunit/vendor/bin/phpunit --testsuite=core-extensions (if needed) 

This way those jobs can be also executed in parallel