Reorganize ecmascript-runtime-client to tolerate more core-js versions.
Reorganize ecmascript-runtime-client to tolerate more core-js versions.

By not implicitly assuming a particular version of core-js (by importing
specific modules), we can avoid the problems reported in #8699.

Fixes #8699.

Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor