[wildcards] Consider reporting UNUSED_CATCH_STACK for stack wildcard params

[pq]

Follow-up from: #55721 (comment), It'd be nice to have a fix (or at least assist) that removes the unnecessary stack catch in code like:

try { } catch(e, _) {
  print(e);
}

producing:

try { } catch(e) {
  print(e);
}

@bwilkerson: if this is a fix, I guess we'd want a diagnostic for what's essentially dead code?

[pq]

Question: do we want to start reporting UNUSED_CATCH_STACK for the wildcard case?

For example:

try { } catch(e, _) {
  print(e);
}

/cc @kallentu @bwilkerson

[bwilkerson]

That seems reasonable to me. There's no value that I can see to having a wildcard as a stack-trace parameter.

[pq]

Note that as we're ignoring underscores today this may cause new diagnostics for folks. (Something to consider.)