Apply basic JNI version script to media JNI libs

Strip all but JNI_OnLoad entrypoints, as this is the only
exported symbol required for JNI interaction. Native methods are
explicitly registered from JNI_OnLoad, and the libraries don't
have downstream native clients that rely on additional exports.

Bug: 306426514
Test: m + presubmit
Flag: EXEMPT bugfix
Change-Id: Ieebe03649bfdc2ced9eb303475877d146989b795