The ibex_pkg.sv file is effectively a "header" with useful defines;
we need them in ibex_tracer_pkg.sv, and in other places around Ibex.
Currently, the dependency between ibex_tracer_pkg.sv and ibex_pkg.sv
wasn't covered in a FuseSoC core file, leading to unstable behavior.
This patch adds this dependency by
- factoring out the ibex_pkg.sv file into a separate core file,
ibex_pkg.core, and
- adding a dependency on the new ibex_pkg core to the ibex_tracer core.
