Rollup merge of #128735 - jieyouxu:pr-120176-revive, r=cjgillot

Add a special case for `CStr`/`CString` in the `improper_ctypes` lint

Revives #120176. Just needed to bless a test and fix an argument, but seemed reasonable to me otherwise.

Instead of saying to "consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct", we now tell users to "Use `*const ffi::c_char` instead, and pass the value from `CStr::as_ptr()`" when the type involved is a `CStr` or a `CString`.

The suggestion is not made for `&mut CString` or `*mut CString`.

r? ``````@cjgillot`````` (since you were the reviewer of the original PR #120176, but feel free to reroll)

compiler/rustc_span/src/symbol.rs

@@ -673,6 +673,7 @@ symbols! {
         crate_visibility_modifier,
         crt_dash_static: "crt-static",
         csky_target_feature,
+        cstr_type,
         cstring_type,
         ctlz,
         ctlz_nonzero,