Move most of Instr and DeoptBase implementations to hir.cpp

Summary:
They shouldn't be in the header as they're not constexpr or templated.  Hide
their implementation details.

Reviewed By: yoney

Differential Revision: D88226979

fbshipit-source-id: 6048697455626725d501ee2c38cd1136d5075a45

Author: alexmalyshev