Switch exported EventEmitter to the C++ implementation

[tsapeta]

Why

I'm switching the exported EventEmitter from the legacy JS implementation to the new one in C++. The previous one will be exported as LegacyEventEmitter and still used in some modules that were not migrated to Expo Modules API (in this case the module object is not an instance of the C++ emitter).

It also renames Subscription type to a more meaningful EventSubscription. I'm intentionally not renaming how the type is re-exported by other packages so I don't introduce a breaking change yet – eventually this type shouldn't be re-exported at all, instead be a common type exported from the expo package.

Test Plan

I went through tests and examples of the modules I changed.

[expo-bot]

The Pull Request introduced fingerprint changes against the base commit: 025f63f

Fingerprint diff

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