Proposal to expose the X_ID_WIDTH parameter in the top-level

[MikeOpenHWGroup]

In #308, @StMiky suggested the following:

One minor change that I would apply is to expose the X_ID_WIDTH parameter in the top-level (cve2_core.sv) instead of hardwiring it in cve2_pkg.sv. This would make it easier to override it based on the desired number of outstanding instructions.

Once #308 is merge or closed, this question will be lost. So the purpose of this Discussion topic is to keep it open.