JDK 14 RFR of JDK-8199424: consider removing ObjectInputStream and ObjectOutputStream native methods

[Joe Darcy]

Hello,

As part of my serialization work, I noticed some "to do" notes in 
ObjectOutputStream.java to get rid of two native methods once the 
integral <-> floating-point bitwise conversion methods 
(Float.floatToIntBits, etc.) were intrinsified. That intrinsification 
occurred many releases back and the recommended cleanup can be done now. 
Pre-existing bug for this issue:

      JDK-8199424 : consider removing ObjectInputStream and 
ObjectOutputStream native methods
     http://cr.openjdk.java.net/~darcy/8199424.0/

Note the logic controlling for copying the float bytes is the same as 
the logic for copying the int bytes as both int and float are 4 bytes, 
same relationship between the copying of double and long bytes.

The serialization regression tests pass with this change. I have not 
attempted to benchmark any speed differences with and without the 
cleanup, but would welcome such an experiment being done.

Thanks,

-Joe