Don't export `.devcontainer`, it's not needed for composer based installation

- reset docs to master before building DTD entities from them
- use symfony Finder to remove all generated files, instead of glob to remove some of them
- less spammy log output (unless --verbose is passed)
- more detailed error messages

I'm planning on refactoring this code, let's get a trivial change out of the way first

Currently we're treating `null` and `false` as special cases, adding and removing them at various points in the process; this results in the return type list being `sorted(types-except-null) + null`. I want to remove the special-case magic, which will have the side effect of changing the return type to `sorted(types)`. I'm pulling that out into a separate PR because it makes the future PR easier to understand, and I also think it's valid to do this by itself

Before:
- When scanning for unsafe functions, check phpdoc type and phpstan type
- When writing wrappers, _occasionally_ check if default value is `null` and infer nullability at the last minute

After:
- When scanning for unsafe functions, check phpdoc type, phpstan type, and default value

Special-cases to handle 7.X-era bugs are no longer needed

Evidence that these cases are redundant: removing them doesn't affect the generated code

When something goes wrong, the stack trace contains ~10,000 lines of spam, often repeated several times over, which makes it hard to find the actual error

Rather than "always strip false/null from return types, and then add them back when the function is non-nullsy / non-falsy", we can reduce complexity by "leave return types alone, strip them only when needed"

This results in no chanes to generated files, but makes future development simpler

The minimalist pass-through stubs we used originally would sometimes behave differently and not actually pass things through as intended D: