Refactor subclassing of RCTEventEmitter

[cipolleschi]

Summary:
This Diff remove the assert on the initializer in the EventEmitter in place of a more idiomatic check when the method is invoked.

It aims to solve an internal error and promotes best practices for the iOS platform.

Changelog:

[iOS][Changed] Refactor RCTEventEmitter initialization

Differential Revision: D40762253

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D40762253

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	7,068,113	+0
android	hermes	armeabi-v7a	6,440,497	+0
android	hermes	x86	7,483,431	+0
android	hermes	x86_64	7,342,828	+0
android	jsc	arm64-v8a	8,933,067	+0
android	jsc	armeabi-v7a	7,667,418	+0
android	jsc	x86	8,993,443	+0
android	jsc	x86_64	9,472,201	+0

Base commit: dac6806
Branch: main

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: dac6806
Branch: main

[pull-bot]

PR build artifact for 674b2a2 is ready.
To use, download tarball from "Artifacts" tab in this CircleCI job then run yarn add <path to tarball> in your React Native project.

[pull-bot]

PR build artifact for 674b2a2 is ready.
To use, download tarball from "Artifacts" tab in this CircleCI job then run yarn add <path to tarball> in your React Native project.

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D40762253

[pull-bot]

PR build artifact for 621cc6f is ready.
To use, download tarball from "Artifacts" tab in this CircleCI job then run yarn add <path to tarball> in your React Native project.

[pull-bot]

PR build artifact for 621cc6f is ready.
To use, download tarball from "Artifacts" tab in this CircleCI job then run yarn add <path to tarball> in your React Native project.

[react-native-bot]

This pull request was successfully merged by @cipolleschi in 25a0052.

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