Further linking ideas (speculative)

[acl-cqc]

Not a tracking issue as these are not currently planned, but for consideration....

• We may want some Linking: temporary publicity #2766 (but one of the options is to do nothing in hugr and leave to tket2).
• Allow specifying a set of which public functions to add. (Currently defaults to all of them, for link_hugr, or none, for insert_link_hugr - which we treat as minimal and include the reachable ones)
• OnMultiDefn / OnNewFunc etc. could be stored in a map from name (rather than one for all names)
• a rename_map: HashMap<String, String> to apply to new functions before insertion/resolution (useful for HugrViews, but not really Hugrs, where you could just apply the renames first)
• For insert_link_hugr, make public functions added (because they were called from the entrypoint) into private ones...that's probably a variant of OnNewFunc
• Option to convert Defns to Decls? (Is that an OnNewFunc ?)