Update Rollup and related plugins to their most recent versions (#24916)

Update Rollup and related plugins to their most recent versions +
resolve any breaking changes/deprecations/etc along the way. I made each
change piece by piece, so the commit history tells a pretty good story
of what was changed where/how/why.

fixes https://github.com/facebook/react/issues/24894

For the full deepdive/context, see:

- https://github.com/facebook/react/issues/24894

The inspiration for this came from @jasonwilliams 's PR for attempting
to add sourcemap output support to React's builds:

- https://github.com/facebook/react/issues/20186
  - https://github.com/facebook/react/pull/21946

But I figured that it would be useful to minimise the scope of changes
in that PR, and to modernise the build tooling along the way.

If any of these updates rely on a node version later than `10.x`, then
the following PR may have to land first, otherwise things might break on
AppVeyor:

- https://github.com/facebook/react/issues/24891
  - https://github.com/facebook/react/pull/24892

Co-authored-by: Sebastian Markbage <sebastian@calyptus.eu>