Update all node engines 12+ (v3)

Major breaking change for all packages, but <= v10 has been EOL for some time. This allows us to delete the core-js polyfills as well.

TODO:

[ ] Update CHANGELOG.md* with your change (include reference to issue & this PR)
[ ] Make sure all of the significant new logic is covered by tests
[ ] Rebase your changes on master so that they can be merged easily
[ ] Make sure all tests and linter rules pass

*Make sure changelog entries note which project(s) has been affected. See older entries for examples on what this looks like.

apollographql / apollo-tooling