[WIP] custom jest output matchers

[julienp]

This shows a custom jest test matchers that know about Outputs.

expect(...).apply(applyFn) takes a callback that's meant to work like Output.apply. Internally it translates to a promise for jest so we don't have to deal with done().

expect(...).toEqualOutputOf(...) can be used to easily check the resolved value of an output.

We could ship these matchers in a @pulumi/jest-matchers library.

Example output for failures:

(line numbers are wrong, but this is unrelated to the PR)

[julienp]

I didn't extend the expect type to know about our matchers, with that we won't need the cast to any here.