Infinite scroll on the page with a lot flags makes the browser really slow and choppy

[vlad-ko]

What product do you want to improve?
Codecov UI

Is your feature request related to a problem? Please describe.
We have a customer that has 700+ flags, when they attempt to scroll the page to the bottom it becomes really slow and choppy. Direct quote:
The batching feels very small and choppy though and I don't think I would ever try to make it to the bottom.

Describe the solution you'd like
Maybe we should do a good ol' pagination for this case instead of the "infinite scroll"?

Describe alternatives you've considered
Any other option to improve performance is OK.

Additional context
Related to: https://github.com/codecov/internal-issues/issues/453