Show env normalization differences under two solvers

[adwinwhite]

First step for param_env normalization future compat warning. zulip thread

I didn't put the check directly in param_env query because normalize_param_env_or_error has some adjustments on the predicates: elaboration and outlive predicates manipulation. I'd have to replicate these in param_env to compare normalized predicates properly.
The downside of putting the check inside normalize_param_env_or_error is that it's used in more than param_env query. It's also used in compare_impl_item and several other places. I'm not sure if this is desired.

I didn't bless tests since the hard error will be changed to lint later.
Blessed tests to demonstrate the changes.

And there's one test about const generics I don't know how to fix.
Canonicalizer for the next solver will replace ParamConst with PlaceholderConst, but it still uses the same try_evaluate_const internally and process_obligation doesn't like PlaceholderConst.

r? @lcnr

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor