PageView: use BigAutoField for primary key (#9670)
How to deploy
We create page views on 404 and on page views (duh),
so while we do the migration this may slow down
doc serving (specially on .com where we have this feature enable for
everyone), so in order to avoid that we need to disable page views
while we do the migration.
Luckily we already have a feature flag for that:
https://github.com/readthedocs/readthedocs.org/blob/a09bc1a976a93bcc3f987fa0a052901f0065619f/readthedocs/projects/models.py#L1897-L1900
ref https://github.com/readthedocs/readthedocs.org/issues/9492
