Nativehelper: Remove static locals for field and method IDs.

This commit replaces static locals with lazy initialization functions so
that field and method IDs can be updated between different VM instances.
It also adds a clear() function to reset the state.

Bug: 65522645
Test: m
Test: m test-art-host
Change-Id: I340cc2ced6b2e5bcd541f1d7b9741574e37c27eb
5 files changed