docs: correct spelling typos in comments and doc strings (#8263)

Fix several spelling errors found in comments and documentation:
- mulithreading -> multithreading (tcp_shutdown.rs)
- succeded -> succeeded (signal/windows/sys.rs)
- implementor/implementors -> implementer/implementers (multiple files)

Co-authored-by: maxtaran2010 <[email protected]>
Co-authored-by: Claude Sonnet 4.6 <[email protected]>
Co-authored-by: Alice Ryhl <[email protected]>

tokio-util/src/codec/decoder.rs

@@ -47,7 +47,7 @@ pub trait Decoder {
     /// implementation of `decode_eof` to yield an `io::Error` when the decoder
     /// fails to consume all available data.
     ///
-    /// Note that implementors of this trait can simply indicate `type Error =
+    /// Note that implementers of this trait can simply indicate `type Error =
     /// io::Error` to use I/O errors as this type.
     ///
     /// [`FramedRead`]: crate::codec::FramedRead

tokio-util/src/codec/mod.rs

@@ -12,7 +12,7 @@
 //! The following example demonstrates how to use a codec such as [`LinesCodec`] to
 //! write framed data. [`FramedWrite`] can be used to achieve this. Data sent to
 //! [`FramedWrite`] are first framed according to a specific codec, and then sent to
-//! an implementor of [`AsyncWrite`].
+//! an implementer of [`AsyncWrite`].
 //!
 //! ```
 //! use futures::sink::SinkExt;
@@ -43,7 +43,7 @@
 //! # Example decoding using `LinesCodec`
 //! The following example demonstrates how to use a codec such as [`LinesCodec`] to
 //! read a stream of framed data. [`FramedRead`] can be used to achieve this. [`FramedRead`]
-//! will keep reading from an [`AsyncRead`] implementor until a whole frame, according to a codec,
+//! will keep reading from an [`AsyncRead`] implementer until a whole frame, according to a codec,
 //! can be parsed.
 //!
 //!```