Allow Monolog v2 to enable psr/log v2/v3

[dereuromark]

When looking into dependencies, it becomes clear that psr/log v1 is required due to a require-dev (optional) dependendy locking it
We need to prevent this in order to fully test both our min and max promise.

As such, this PR aims to fix it properly - and replaces #1819

Completes #1805

With this PHP7 folks are using psr/log v1, PHP8 folks can use psr/log v2/v3 already.

[oojacoboo]

Is it necessary for this lib to define the psr/log interface dependency in composer.json if the only dependency to this interface exists in a 3rd party lib/dep?

[dereuromark]

Probably not, in that case we could move this also into require-dev and unblock people then fully if no such library is used.
I wonder if "any logger"/"at least one" would still be a good requirement by default though.
Is anyone using this lib without a logger in place at all?

[oojacoboo]

If the code doesn't require the interface, we shouldn't be having it as a dependency. The dependencies should be for the direct use in this lib. I assumed Propel needed that interface for it's own internal logging logic.

If that's not the case, it should be removed entirely, allowing for monolog/monolog to manage it's own dependencies, however necessary.

[dereuromark]

class ConnectionWrapper implements ConnectionInterface, LoggerAwareInterface

so this is quite deeply integrated.

Given that I don't think we can move it into require-dev.

With this PR all constraints are still unblocked as everyone can use the correct psr interfaces as per their needs.
So we should be fine.

[oojacoboo]

The issue is this:

    /**
     * @param \Psr\Log\LoggerInterface $logger
     *
     * @return void
     */
    public function setLogger(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }

https://github.com/php-fig/log/blob/2.0.0/src/LoggerInterface.php

Version 2 there of the LoggerInterface uses union types. That's a PHP 8 feature. Therefore, version 2 and version 3 of this interface cannot be supported without also supporting a min of PHP 8.

[oojacoboo]

This PR is fine though, I agree. #1819 still needs merging as well.