Do not share key mappings with JNI object

The key mapping information between the native key mappings and
the KeyCharacterMap object available in Java is currently shared,
which means that a read can be attempted while it's being modified.

Bug: 274058082
Test: Patch tested by Oppo
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:3d993de0d1ada8065d1fe561f690c8f82b6a7d4b)
Merged-In: I745008a0a8ea30830660c45dcebee917b3913d13
Change-Id: I745008a0a8ea30830660c45dcebee917b3913d13