feat: New MMKV Core and readOnly mode

[mrousavy]

• Updates MMKV core from V1 to V2 (latest) -> this contains a bunch of fixes and improvements
• Adds readOnly / isReadOnly mode to MMKV.

  const storage = new MMKV({
    id: 'some-storage',
    readOnly: true
  })
  const value = storage.getString('key') // <-- works
  storage.set('key', 'value') // <-- throws an error
  storage.isReadOnly // <-- true

• Adds support for 16k page-size on Android