Pin Virtual Thread in class initializer

The class linker can't handle the parking exception currently.
Pinning in class initializer also matches the RI behavior

NO_IFTTT=kCriticalSection is pre-existing in Continuation.java
Flag: com.android.art.flags.virtual_thread_impl_v1
Bug: 445864630
Test: 2395-virtual-thread-class-initializer

Change-Id: I36cb2fa6d1f9515ed00bb5c032484b39f4cc1b05