[WIP] Add js target

[hujim]

Ready for a pass as the changes are non-trivial. Reviewing by may should help.

1. Add JS target.
2. Fix test names to non back-ticks for common tests can't have them for JS test support.
3. Updated to use new coroutine testing library methods.
4. Handle different results ErrorLoggingInterceptor for jsTargets in tests.
5. Add JS WorkflowIdentifierTypeNamer to handle JS class comparison.

Will clean up commits when ready

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[hujim]

Rebased and reopened as a new PR here: https://github.com/square/workflow-kotlin/pull/887