Test fixes from 4.4.2 to 5.x merge

[escopecz]

Q	A
Bug fix? (use the a.b branch)	[Y]
New feature/enhancement? (use the a.x branch)	[N]
Deprecations?	[N]
BC breaks? (use the c.x branch)	[N]
Automated tests included?	[N]
Related user documentation PR URL	/
Related developer documentation PR URL	/
Issue(s) addressed	Fixes #11402

Description:

#11196 added dynamic table prefix to the tests for a good reason. However, it means that the cache must be cleared before every test execution. A developer can run test(s) many times per day and building the cache takes tens of seconds. That means it's a big lose of time.

This PR changes it to static prefix which can be defined by .env(.dist) file or by defining env var in the phpunit command execution itself. There is small chance that the developer uses the same table prefix on local, production and test environment so the problem with hard-coded prefixes should be discovered in some environment.

We had problem in #11438 that the CI tests were still failing even after the static table prefix. So this PR also contains unified loading of the env file and setting MAUTIC_ENV=test in the CI which actually fixed the issue as after that the config_test.php was properly loaded.

Steps to test this PR:

1. No testing is needed as no production code was changed. Just changes in how we run tests. So review the changes and check the CI that it is green and the output for PHPUNIT tests makes sense.

[codecov]

Codecov Report

Merging #11476 (233e4e7) into 4.4 (dedf40b) will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                4.4   #11476   +/-   ##
=========================================
  Coverage     49.36%   49.37%           
  Complexity    35401    35401           
=========================================
  Files          2144     2144           
  Lines        105532   105532           
=========================================
+ Hits          52101    52102    +1     
+ Misses        53431    53430    -1     

Impacted Files	Coverage Δ
...eBundle/EventListener/DoctrineEventsSubscriber.php	74.54% <0.00%> (+1.81%)	⬆️

[mollux]

Fix is good to solve the seen issue.

I still don't get how the MAUTIC_ENV change is needed, as

• SYMFONY_ENV is set and will be used to set MAUTIC_ENV if not defined (see https://github.com/mautic/mautic/blob/5.x/app/AppKernel.php#L38)
• the \Symfony\Bundle\FrameworkBundle\Test\KernelTestCase::createKernel() defaults to test, which will create the AppKernel with the test environment
• the \AppKernel::getCacheDir() uses the environment to determine the cache dir.
• Mautic console depends on the SYMFONY_ENV var to determine the environment, see https://github.com/mautic/mautic/blob/5.x/bin/console#L29
• the content of the .env and .env.dist files is correct

So even is there is logic that would boot mautic with the wrong env, it would only fill up the cache for the wrong env.
PHPUnit will alwas use the test env (unless defined otherwise, but this isn't the case)

I may dive deeper to really understand this issue, as we can't reproduce this on 4.x or local, and there is no substantial change in 5.x branch that can explain this.
It looks like there is an external factor (github action, ...) that results in this funky situation.

But as this solves this weird situation, I don't see any issue merging this.