test: observe native execution callback verification cost

tests/fixtures/public-safety-access/execution-observer-worker.tsadded+5-0

Changes to tests/fixtures/public-safety-access/execution-observer-worker.ts

		@@ -0,0 +1,5 @@
	1	+self.onmessage = ({ data }) => {
	2	+ if (data !== 'emit') return
	3	+ self.onmessage = null
	4	+ for (const kind of ['event', 'result', 'finished', 'unrecognized']) self.postMessage({ kind, payload: 'private-callback-payload', bytes: new Uint8Array([1, 2, 3]) })
	5	+}