Create a transient SELinux domain where system_server can perform
certain JIT setup. The idea is that system_server will start in the
system_server_startup domain, setup certain JIT pages, then perform a
one-way transition into the system_server domain. From that point,
further JITing operations are disallowed.

Bug: 62356545
Test: device boots, no permission errors
Change-Id: Ic55b2cc5aba420ebcf62736622e08881a4779004