Remove dependency on libnativehelper/JniConstants.h

Remove unused references to JniConstants.h.

Add jclass value caching in SharedMemory and StrictJarFile as present
for other classes here.

Lightly tidy up JNI code touched.

Bug: 119840313
Test: atest cts/tests/tests/os
Test: tests/tests/util/src/android/util/cts/StrictJarFileTest.java

Change-Id: I0be0fecdd9c7f9dd32cf588ed79060f0ce268588