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_builtin_macros/src/concat_bytes.rs

@@ -55,7 +55,7 @@ fn invalid_type_err(
         Ok(LitKind::Int(_, _)) => dcx.emit_err(ConcatBytesNonU8 { span }),
         Ok(LitKind::ByteStr(..) | LitKind::Byte(_)) => unreachable!(),
         Ok(LitKind::Err(guar)) => guar,
-        Err(err) => report_lit_error(&cx.sess.parse_sess, err, token_lit, span),
+        Err(err) => report_lit_error(&cx.sess.psess, err, token_lit, span),
     }
 }