Exception clean up

[patrickkusebauch]

Closes #988

• Clean up unused exceptions
• Ensure all custom exceptions implement ExceptionInterface
• Ensure all custom exceptions use a static factory method
• Replace overly generic or vague exceptions with dedicated exceptions or better fitting ones, especially ShouldNotHappenException
• Add helpful error messages to raised exception
• Declare which exceptions are expected to be thrown using @throws in the doc block
• Psalm config
• PHPStan config

[patrickkusebauch]

Notes:

• YmlFileLoader seems to be unused?
• Sometimes exceptions are thrown in constructors of classes that are created by Symfony DIC. Therefore, they are practically unchecked.
• Psalm does not support @throws void for cases you are sure the exception cannot be thrown (see: Idea: @psalm-never-throw, alike to @psalm-pure, but promises to not throw/warn vimeo/psalm#2912). So this bloats the Psalm baseline file
• PHPStan baseline has cases I just could not be bothered to fix. Either would require extensive refactoring or just cannot be easily suppressed inline.
• I am not any good at writing user-friendly exception messages. This can be done in another pass by someone else.
• BC break, because new/different/previously unexposed exceptions are now exposed in the contract.

[dbrumann]

Thanks a lot! That is really helpful. I didn't know phpstan could report unchecked exceptions. I really like that as well 👍