Update dev dependency "rollup"

[mikeharder]

Our repo is currently using rollup@1.32.1. A new major version rollup@2.0.0 was released on 3/6/2020. The upgrade may require significant changes.

https://github.com/rollup/rollup/blob/master/CHANGELOG.md#200

[willmtemple]

(CC @bterlson for discussing Node 8 support)

Major blocker here is

Rollup now requires at least Node 10 to run, or a sufficiently modern browser (#3346)

In order to make the migration to Rollup 2 we'd need to move the Linux pipeline build off of Node 8. Nothing else in the changelog really sticks out at me, but there's always a chance there would be other complications too.

@mikeharder @praveenkuttappan One thing that could work here is if we could do all the builds in CI with Node 12 and then only do test runs with our different node versions. Is this something we can do easily or is everything in the pipeline run with the same base node configuration.

[mikeharder]

@mikeharder @praveenkuttappan One thing that could work here is if we could do all the builds in CI with Node 12 and then only do test runs with our different node versions. Is this something we can do easily or is everything in the pipeline run with the same base node configuration.

This is already done: #8804

[witemple-msft]

Currently blocked on an upstream bug in @rollup/plugin-commonjs: rollup/plugins#743

Migrating to rollup 2 and the newer versions of plugin-commonjs will ease the transition to the shared rollup configuration, so this is related to that as well.

[maorleger]

Spoke to @witemple-msft - he's looking into this so he OK'd assigning it to him for now

[jeremymeng]

closing in favor of bot-auto-created #19235.