Remove JniStringCache

Unfortunately the overhead from JNI functions was found to be unaffordable high.
The root causes are unfixable.
See investigation in b/443641982.

I may revisit this problem with a Java-side cache, such as by resuming work on ag/35275812.

Bug: 443641982
Bug: 442140362
Flag: android.os.parcel_string_cache_enabled
Change-Id: Ie77174731976c4adf2754134596df8a8f567a19e