Follow up to RuntimeWorkers change

[samtstern]

Description

This is a follow up to #1733 to make some of the changes that @yuchenshi asked for. This was a nice and productive rabbit hole.

Changes include:

• Make FunctionsEmulator no longer rely on the options object
• Change static methods from FunctionsEmulator that were only static for testing purposes
• Move all of the logging code into EmulatorLogger where it belongs
• Assign the socketPath for HTTPS functions before the function runs so that we don't have to
  wait async for it to bubble up.
• Remove the waitForSystemLog function from the worker class, it's not needed anymore.
• Remove waiting for ready from background functions where it's not needed.

Scenarios Tested

In addition to making the test suite run, I tested that these functions all work as expected:

exports.helloWorld = functions.https.onRequest(async (req, res) => {
    res.json({
        hello: 'world',
        date: new Date()
    });
});

exports.firestoreWriter = functions.https.onRequest(async (req, res) => {
    await admin.firestore().doc('foo/bar').set({
        date: new Date()
    });
});

exports.firestoreReader = functions.firestore.document('foo/bar').onWrite(async (change, ctx) => {
    console.log("Firestore Write:", JSON.stringify(change.after.data()));
});

Sample Commands

N/A

[samtstern]

All of this code is just moved over from FunctionsEmulator. No changes.

[samtstern]

By making this function not static we were able to just used the trigger definitions held on the emu instance rather than waiting for a log.

[samtstern]

This is the code that was moved to EmulatorLogger

[coveralls]

Coverage increased (+0.2%) to 66.248% when pulling d5e295b on ss-runtime-workers-follow-up into 52281c0 on master.