Split the zygote logic out of android.os.Process into a new ZygoteProcess class.

There is no functional change. This is to support adding new types of zygotes
that all operate using the same protocol.

Bug: 21643067
(cherry picked from commit 94e824bc1b5f83024b7c9a228a8f2d0cd1347d11)
(cherry picked from commit 96b49848e7784bc4b40ffd01e2524461e1efcab7)

Change-Id: I2e12057e4c2e7567f909d699b487e70b1664cca8
4 files changed