Add Async/await tests for Functions

[paulb777]

• Add Async/await tests for Functions
• Add commented out CocoaPods testspecs for Functions Swift integration tests
• Add watchos to pod lib lint CI

I initially thought that CocoaPods was necessary to test async/await because of the global SPM minimum os version, but whether or not async/await tests get run is enabled by the test target's device.

Fix #8955 - a combine test build issue introduced in #8957

[google-oss-bot]

	1 Warning
⚠️	Did you forget to add a changelog entry? (Add #no-changelog to the PR description to silence this warning.)

Generated by 🚫 Danger

[google-oss-bot]

Coverage Report

Affected SDKs

• FirebaseDatabase-iOS-FirebaseDatabase.framework

  SDK overall coverage changed from 56.63% (f023aa5) to 56.79% (e0d69a0) by +0.16%.

  Filename	Base (f023aa5)	Head (e0d69a0)	Diff
  FSRWebSocket.m	38.73%	40.82%	+2.10%

Test Logs

• Base (f023aa5b): https://github.com/firebase/firebase-ios-sdk/actions/runs/1449664764
• Head (e0d69a04): https://github.com/firebase/firebase-ios-sdk/actions/runs/1451127607

[maksymmalyhin]

👍 Nice, thank you Paul!