rename: crate::wchar::prelude -> crate::prelude

Having the prelude in wchar is not great. The wchar module was empty
except for the prelude, and its prelude included things from wutil.

Having a top-level prelude module in the main crate resolves this. It
allows us to completely remove the wchar module, and a top-level prelude
module makes more sense conceptually. Putting non-wchar things into the
prelude also becomes more sensible, if we ever want to do that.

Closes #12182

src/wutil/dir_iter.rs

@@ -328,7 +328,7 @@ fn next(&mut self) -> Option<Self::Item> {
 #[cfg(test)]
 mod tests {
     use super::{DirEntryType, DirIter};
-    use crate::wchar::prelude::*;
+    use crate::prelude::*;
     use fish_wchar::L;
     use nix::sys::stat::Mode;
     use std::fs::File;

src/wutil/gettext.rs

@@ -2,7 +2,7 @@
 
 #[cfg(feature = "localize-messages")]
 use crate::env::{EnvStack, Environment};
-use crate::wchar::prelude::*;
+use crate::prelude::*;
 use once_cell::sync::Lazy;
 
 #[cfg(feature = "localize-messages")]
@@ -386,8 +386,8 @@ macro_rules! wgettext_fmt {
 #[cfg(test)]
 mod tests {
     use super::LocalizableString;
+    use crate::prelude::*;
     use crate::tests::prelude::*;
-    use crate::wchar::prelude::*;
 
     #[test]
     #[serial]

src/wutil/mod.rs

@@ -475,8 +475,8 @@ mod tests {
     use super::{normalize_path, wbasename, wdirname, wstr_offset_in, wwrite_to_fd};
     use crate::common::bytes2wcstring;
     use crate::fds::AutoCloseFd;
+    use crate::prelude::*;
     use crate::tests::prelude::*;
-    use crate::wchar::prelude::*;
     use libc::{O_CREAT, O_RDWR, O_TRUNC, SEEK_SET};
     use rand::Rng;
     use std::{ffi::CString, ptr};

src/wutil/wcstoi.rs

@@ -1,5 +1,5 @@
 pub use super::errors::Error;
-use crate::wchar::prelude::*;
+use crate::prelude::*;
 use num_traits::{NumCast, PrimInt};
 use std::default::Default;
 use std::iter::{Fuse, Peekable};