Throw exceptions when memory allocations fail.

[juergw]

ScopedByteArrayRO may need to allocate memory, and that allocation may fail. When this happens, which should throw an error.

We also add a check before that if the input is null, and throw an exception in that case. This preserves the current behavior. Without that, an out of memory exception would be thrown if the input is null, which is not what we want.

[juergw]

I also remove some logging of private keys.

[prbprbprb]

I also remove some logging of private keys.

Note that JNI_TRACE compiles to nothing unless conscrypt::trace::kWithJniTrace is true at compile time, so there should be no accidental leakage of keys.