Clean up some non-mod-rs stuff.
This includes the following:
- Remove unused `non_modrs_mods` from `ParseSess` which as only used for feature gate diagnostics.
- Remove the vestiges of the feature gate tests in `test/ui`, they were only partially removed during stabilization.
- Fix the run-pass test, it was accidentally removed during stabilization.
- Add a ui test to verify error behavior for missing inline-nested mods.
- Add some tests for `#[path]` for inline-nested mods (both mod and non-mod-rs).
- Enable the diagnostic tests on windows, they should be fixed by #49478.
cc @cramertj
reword #[test] attribute error on fn items
fix of [#55787](https://github.com/rust-lang/rust/issues/55787)
Reworded error message from "#[test] attribute is only allowed on fn items" to "#[test] attribute is only allowed on non associated functions"
in which the E0618 "expected function" diagnostic gets a makeover
A woman of wisdom once told me, "Better late than never." (Can't reopen the previously-closed pull request from six months ago [due to GitHub limitations](https://github.com/rust-lang/rust/pull/51098#issuecomment-437647157).)
Now the main span focuses on the erroneous not-a-function callee, while showing the entire call expression is relegated to a secondary span. In the case where the erroneous callee is itself a call, we
point out the definition, and, if the call expression spans multiple lines, tentatively suggest a semicolon (because we suspect that the "outer" call is actually supposed to be a tuple).


The new `bug!` assertion is, in fact, safe (`confirm_builtin_call` is only called by `check_call`, which is only called with a first arg of kind `ExprKind::Call` in `check_expr_kind`).
Resolves#51055.
r? @estebank
More precise spans for temps and their drops
This PR has two main enhancements:
1. when possible during code generation for a statement (like `expr();`), pass along the span of a statement, and then attribute the drops of temporaries from that statement to the statement's end-point (which will be the semicolon if it is a statement that is terminating by a semicolon).
2. when evaluating a block expression into a MIR temp, use the span of the block's tail expression (rather than the span of whole block including its statements and curly-braces) for the span of the temp.
Each of these individually increases the precision of our diagnostic output; together they combine to make a much clearer picture about the control flow through the spans.
Fix#54382