This command will cause `pulumi policy publish` to behave in much the
same way `pulumi up` does -- if the policy program is in TypeScript, we
will use ts-node to attempt to compile in-process before executing, and
fall back to plain-old node.
We accomplish this by moving `cmd/run/run.ts` into a generic helper
package, `runtime/run.ts`, which slightly generalizes the use cases
supported (notably, allowing us to exec some program outside of the
context of a Pulumi stack).
This new package is then called by both `cmd/run/index.ts` and
`cmd/run-policy-pack/index.ts`.
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