Implement RunPlugin for NodeJS. This follows a similar path as the rest
of the language runtime does, spawning a NodeJS program, which in turn
runs the plugin itself. The run-plugin code was cribbed from
run-policy-pack, which works similarly.
Note that this means that in addition to a recent language runtime, this
also requires the plugin to reference a recent version of the Pulumi
SDK. Since the main purpose of implementing this is supporting a new
feature that should be okay though.
Fixes https://github.com/pulumi/pulumi/issues/17663