Avoid naming variables str

This renames variables named `str` to other names, to make sure `str`
always refers to a type.

It's confusing to read code where `str` (or another standard type name)
is used as an identifier. It also produces misleading syntax
highlighting.

std/src/process.rs

@@ -1283,13 +1283,13 @@ impl fmt::Debug for Output {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         let stdout_utf8 = str::from_utf8(&self.stdout);
         let stdout_debug: &dyn fmt::Debug = match stdout_utf8 {
-            Ok(ref str) => str,
+            Ok(ref s) => s,
             Err(_) => &self.stdout,
         };
 
         let stderr_utf8 = str::from_utf8(&self.stderr);
         let stderr_debug: &dyn fmt::Debug = match stderr_utf8 {
-            Ok(ref str) => str,
+            Ok(ref s) => s,
             Err(_) => &self.stderr,
         };
 

std/src/sys/pal/windows/process.rs

@@ -142,11 +142,11 @@ impl AsRef<OsStr> for EnvKey {
     }
 }
 
-pub(crate) fn ensure_no_nuls<T: AsRef<OsStr>>(str: T) -> io::Result<T> {
-    if str.as_ref().encode_wide().any(|b| b == 0) {
+pub(crate) fn ensure_no_nuls<T: AsRef<OsStr>>(s: T) -> io::Result<T> {
+    if s.as_ref().encode_wide().any(|b| b == 0) {
         Err(io::const_error!(ErrorKind::InvalidInput, "nul byte found in provided data"))
     } else {
-        Ok(str)
+        Ok(s)
     }
 }
 

std/src/sys_common/wtf8.rs

@@ -204,8 +204,8 @@ impl Wtf8Buf {
     ///
     /// Since WTF-8 is a superset of UTF-8, this always succeeds.
     #[inline]
-    pub fn from_str(str: &str) -> Wtf8Buf {
-        Wtf8Buf { bytes: <[_]>::to_vec(str.as_bytes()), is_known_utf8: true }
+    pub fn from_str(s: &str) -> Wtf8Buf {
+        Wtf8Buf { bytes: <[_]>::to_vec(s.as_bytes()), is_known_utf8: true }
     }
 
     pub fn clear(&mut self) {