Make initializeApp idempotent

[Feiyang1]

initializeApp now can be called more than once and returns the same instance as long as using the same options and config. It should make the devX more friendly with HMR and other use cases.

No need to wrap initializeApp() in the if block anymore:

// the if condition can be safely removed now
// if(getApps().length === 0) {
    initializeApp({...})
// }

[changeset-bot]

🦋 Changeset detected

Latest commit: 86e4f91

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

This PR includes changesets to release 15 packages

Name	Type
@firebase/util	Minor
@firebase/analytics	Patch
@firebase/app-check	Patch
@firebase/app	Patch
@firebase/component	Patch
@firebase/database	Patch
firebase	Patch
@firebase/firestore	Patch
@firebase/installations	Patch
@firebase/messaging	Patch
@firebase/performance	Patch
@firebase/remote-config	Patch
@firebase/rules-unit-testing	Patch
@firebase/storage	Patch
@firebase/functions	Patch

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[github-actions]

Changeset File Check ⚠️

• Warning: This PR modifies files in the following packages but they have not been included in the changeset file:

  • @firebase/app-compat
  • @firebase/app-exp

  Make sure this was intentional.

• Package @firebase/util has a minor bump which requires an additional line to bump the main "firebase" package to minor.