DB: denormalize has good build on `Project`

[humitos]

Instead of keeping this complexity around, I think it's a lot easier to add a field Project.has_good_build that's updated when the first successful build happens and use that field to filter them here.

The query will be instant and a lot easier to understand.

Originally posted by @humitos in #12385 (review)

[stsewd]

The annotation for has_good_build is performing good on all cases, and it's only done for 15 projects at a time.

readthedocs.org/readthedocs/projects/querysets.py

Lines 155 to 157 in 63e16bd

	return self.annotate(
	_has_good_build=Exists(Build.internal.filter(project=OuterRef("pk"), success=True))
	)

Don't think we have the need to normalize this field for now.