Check printf parameter types

[schlndh]

Motivation: I refactored code to use BcMath\Number instead of float, and I didn't notice a printf usage with %f, which lead to incorrect result. PHPStan didn't complain, because BcMath\Number has __toString().

Here is an executed version of the test file: https://3v4l.org/3pXMc

I left some things for possible future PRs to keep things simple:

• Strict mode: enforce int for %d, int|float for %f, __stringandstringable for %s. This may be too strict for default PHPStan, but IMO it would be a good candidate for phpstan-strict-rules.
• Handle multiple possibilities for format string.
• Add support for vprintf/vsprintf.

[ondrejmirtes]

I'm a bit skeptical here. I think that a lot more types should be allowed in the placeholders. There are probably many combinations allowed by PHP but disallowed by this new rule. For example - you're allowing only int in %d but it also allows float: https://3v4l.org/XOB5o

[ondrejmirtes]

If it's not the case, the message 'Placeholder #1 of function printf expects int, PrintfParamTypes\\FooStringable given' (the first assertion) is misleading.

[schlndh]

I improved the error messages. The rule allows passing float to %d (and hopefully other meaningfully usable cases as well), it was just not clear from the previous (quite poor) error messages.

Some edge-cases:

• One parameter can be used by multiple placeholders. I decided to generate a separate error for each placeholder, instead of trying to combine them into one (especially since the placeholder is now a part of the error message).
• One placeholder can reference multiple parameters (e.g. %*.*f - the *s each consume a positional parameter). So for cases where a * is used, I clarified whether it's the width, precision or value that's the problem. E.g. "%*.*f" (width).

Tests (8.2, ubuntu-latest) fail, but it seems to be unrelated to my PR ("UnitEnum" could not be found in the located source).

[ondrejmirtes]

Thank you!