Fix db.useEmulator

[schmidt-sebastian]

We need to invoke repoManagerApplyEmulatorSettings with db._repoInternal as db._repo starts the WebSocket connection if it hasn't yet been started and applies the production host.

Also random unrelated cleanup.

Fixes #4811

[changeset-bot]

🦋 Changeset detected

Latest commit: a829398

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
@firebase/database	Patch
firebase	Patch
@firebase/rules-unit-testing	Patch

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[yuchenshi]

Confirmed locally that this fixes a race condition

[google-oss-bot]

Binary Size Report

Affected SDKs

• @firebase/database

  Type	Base (d442eb2)	Head (28070a9)	Diff
  browser	291 kB	291 kB	-14 B (-0.0%)
  esm2017	261 kB	261 kB	-8 B (-0.0%)
  main	294 kB	294 kB	-14 B (-0.0%)
  module	291 kB	291 kB	-14 B (-0.0%)

• @firebase/database-compat

  Type	Base (d442eb2)	Head (28070a9)	Diff
  browser	84.3 kB	84.3 kB	-16 B (-0.0%)
  main	99.7 kB	99.7 kB	-22 B (-0.0%)
  module	84.3 kB	84.3 kB	-16 B (-0.0%)

• @firebase/database-exp

  Type	Base (d442eb2)	Head (28070a9)	Diff
  browser	242 kB	242 kB	-8 B (-0.0%)
  main	273 kB	273 kB	-14 B (-0.0%)
  module	242 kB	242 kB	-8 B (-0.0%)

• firebase

  Type	Base (d442eb2)	Head (28070a9)	Diff
  firebase-database.js	183 kB	183 kB	+2 B (+0.0%)
  firebase.js	869 kB	869 kB	+2 B (+0.0%)

Test Logs

• Base (d442eb28): https://github.com/firebase/firebase-js-sdk/actions/runs/775866025
• Head (28070a9d): https://github.com/firebase/firebase-js-sdk/actions/runs/778999633