Rename all ParseSess variables/fields/lifetimes as psess.

Existing names for values of this type are `sess`, `parse_sess`,
`parse_session`, and `ps`. `sess` is particularly annoying because
that's also used for `Session` values, which are often co-located, and
it can be difficult to know which type a value named `sess` refers to.
(That annoyance is the main motivation for this change.) `psess` is nice
and short, which is good for a name used this much.

The commit also renames some `parse_sess_created` values as
`psess_created`.

compiler/rustc_hir_analysis/src/check/errs.rs

@@ -70,7 +70,7 @@ fn handle_static_mut_ref(
         } else {
             (errors::StaticMutRefSugg::Shared { span, var }, "shared")
         };
-        tcx.sess.parse_sess.dcx.emit_err(errors::StaticMutRef { span, sugg, shared });
+        tcx.sess.psess.dcx.emit_err(errors::StaticMutRef { span, sugg, shared });
         return;
     }