Rollup merge of #124000 - compiler-errors:sugg-tweaks, r=wesleywiser

Use `/* value */` as a placeholder

The expression `value` isn't a valid suggestion; let's use `/* value */` as a placeholder (which is also invalid) since it more clearly signals to the user that they need to fill it in with something meaningful. This parallels the suggestions we have in a couple other places, like arguments.

We could also print the type name instead of `/* value */`, especially if it's suggestable, but I don't care strongly about that.

Author: GuillaumeGomez