[HW Parameters] Expand ParamVerbatimAttr to allow subexpr attribute substitution

[lattner]

ParamVerbatimAttr should someday support the same complement of features as sv.verbatim.expr, but in the parameter domain. In particular, it should take an optional list of attributes and substitute them into {{0}} positions. These should be attributes, allowing the use of #hw.param.decl.ref (and other derived expressions) so you can use a macro with arguments in a parameter list.

This is not high priority to me personally, just capturing this as a "nice to have" enhancement in case someone is interested in picking it up.