Rollup merge of #146283 - LorrensP-2158466:resolve-cm-cell, r=petrochenkov

Resolve: (Ref)Cell wrappers to deny mutation during spec resolution.

Introduces wrappers around `Cell` and `RefCell` that only allow mutation when we are not in speculative resolution. This is preparatory work for rust-lang/rust#145108.

It would allow us to make `ImportData` and `ModuleData` sync and send safe.

r? ``@petrochenkov``

Author: matthiaskrgr