feat: unify initial text/html iOS emitting with Android

[szydlovsky]

Summary

After the latest PRs it also came to my mind that Android and iOS emit the initial events a bit differently. If we have some defaultValue set, iOS wouldn't emit text (and would emit html always, even if defaultValue was not set), while Android properly emitted both html and text only if the prop is set.

This PR changes:

• initial recentlyEmittedHtml value so that it doesn't emit with no defaultValue
• sets recentlyEmittedString only if the onChangeText event properly wen through (event emitter was defined). This way text emits if it's different than the initial ""

Test Plan

Run the example iOS app once with no defaultValue and the other time with defaultValue. Observe that in the first scenario no initial events are dispatched, while in the second they are emitted as soon as emitter is ready.

Screenshots / Videos

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Compatibility

OS	Implemented
iOS	✅
Android	✅ (was fine already)