Auto merge of #50197 - nikomatsakis:skolemize-out-of-tcx, r=eddyb

move skolemized regions into global tcx

Experimental branch to move skolemized regions into global tcx. This is probably not what we want long term but may be convenient to unblock @sgrif in the short term.

I'd like to do a perf run, though the main concern I guess would be memory usage.

r? @eddyb