ART: Give JIT thread pool workers a peer

To allow reporting those threads, give JIT pool threads a peer.
This is necessary as the compiler may load classes.

Bug: Bug: 29547798
Bug: 31684920
Test: m ART_TEST_JIT=true test-art-host
Change-Id: I7c8e44132475f38995542da76285ca3dd63c559a
2 files changed