Rollup merge of #66043 - RalfJung:memory-get-raw, r=cramertj

rename Memory::get methods to get_raw to indicate their unchecked nature

Some recent Miri PRs started using these methods when they should not; this should discourage their use.

In fact we could make these methods private to the `interp` module as far as Miri is concerned -- with the exception of the `uninit` intrinsic which will hopefully go away soon. @bjorn3 @oli-obk does priroda need these methods? It would be great to be able to seal them away.