Disable hidden API checks during WellKnownClasses::Init

WellKnownClasses gets handles on hidden methods/fields from an
unattached native thread using JNI. The hidden API logic assumes
these calls are not coming from boot class path and blocks access.
Disable the checks during the Init routing.

Bug: 64382372
Test: make
Change-Id: I53b2c5a29b2b01667a002283b84c6095b37ba724
(cherry picked from commit 8407b4eb)