Add `Array.push` API (#53762)

Summary:

Currently, the size of a jsi `Array` is immutable. Once the `Array` is
created, users can only set the element at an existing index, but not
append to it.

This change adds an `Array::push` API to improve ergonomics.
The default implementation is also provided in `jsi::Runtime`

Changelog: [Internal]

Reviewed By: lavenzg

Differential Revision: D82254334