Add back support for 'method_binding_format' in HostRuntime.cpp

HostRuntime previously had support for specifying a custom
JNI method binding method. This is needed for Robolectric
which renames native methods during its instrumentation process.
This commit restores this support.

Flag: NONE host-only change
Test: m libandroid_runtime, run robolectric tests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:620077d593902a67b4f75f31b557a1246d84c733)
Merged-In: Iea471edc74317dda1e92899d1ad68fa3520b6812
Change-Id: Iea471edc74317dda1e92899d1ad68fa3520b6812