[expo-modules-core] Add stopObserving and startObserving functions

[aleqsio]

Why

Matching iOS implementation for startObserving and stopObserving functions

How

Added calling those functions to CoreModule's EventEmitter class.

Test Plan

Added unit tests.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for npx expo prebuild & EAS Build (eg: updated a module plugin).

[expo-bot]

The Pull Request introduced fingerprint changes against the base commit: 7a547e4

Fingerprint diff

[
  {
    "type": "dir",
    "filePath": "../../packages/expo-audio/ios",
    "reasons": [
      "expoAutolinkingIos"
    ],
    "hash": "f4a3387af1f69703875270f21efb3aa3859ed0f2"
  },
  {
    "type": "dir",
    "filePath": "../../packages/expo-modules-core",
    "reasons": [
      "expoAutolinkingIos",
      "expoAutolinkingAndroid"
    ],
    "hash": "a431fe056acb794845fbca538f52d61ea59f8c4f"
  },
  {
    "type": "dir",
    "filePath": "ios",
    "reasons": [
      "bareNativeDir"
    ],
    "hash": "2e914129beaf1a429014be0c9c0d7d53be9fe82c"
  }
]

---

Generated by PR labeler 🤖

[tsapeta]

We may want to move these tests to https://github.com/expo/expo/blob/main/packages/expo-modules-core/src/__tests__/EventEmitter-test.web.ts

Also notice these silenced tests:

expo/packages/expo-modules-core/src/__tests__/EventEmitter-test.web.ts

Lines 87 to 88 in 3a2579c

	// TODO: Enable these tests once Web supports `startObserving` and `stopObserving`.
	xdescribe('observing', () => {

[aleqsio]

@tsapeta I fixed a failing test case in sensors – think the current test is the expected behaviour, not sure why the expectation was different 5y ago.

[aleqsio]

we could remove it and make it optional

[aleqsio]

After testing this, I can't get the types working if I remove this stub.