[HW] Make "dontTouch" a first-class attribute on operations

It might make sense to add some of the very common attributes on operations in Comb/Seq/HW, like a "dontTouch", an attribute specified in the tables. I suspect that there will me more of these in the future.

Start by locating the operation tables for the Comb, Seq, and HW dialects and reviewing how existing common attributes are represented. Determine the intended scope and semantics of a first-class "dontTouch" attribute, then identify the relevant operation coverage and tests; the issue does not name specific files or define completion criteria.

Written by the indexing model from the issue text.