Change PathLikeWithPosition<P> into a non-generic type and replace ad-hoc Windows path parsing (#15373)

This simplifies `PathWithPosition` by making the common use case
concrete and removing the manual, incomplete Windows path parsing.
Windows paths also don't get '/'s replaced by '\\'s anymore to limit the
responsibility of the code to just parsing out the suffix and creating
`PathBuf` from the rest. `Path::file_name()` is now used to extract the
filename and potential suffix instead of manual parsing from the full
input. This way e.g. Windows paths that begin with a drive letter are
handled correctly without platform-specific hacks.

Release Notes:

- N/A

crates/cli/src/main.rs

@@ -5,14 +5,13 @@ use clap::Parser;
 use cli::{ipc::IpcOneShotServer, CliRequest, CliResponse, IpcHandshake};
 use parking_lot::Mutex;
 use std::{
-    convert::Infallible,
     env, fs, io,
     path::{Path, PathBuf},
     process::ExitStatus,
     sync::Arc,
     thread::{self, JoinHandle},
 };
-use util::paths::PathLikeWithPosition;
+use util::paths::PathWithPosition;
 
 struct Detect;
 
@@ -54,13 +53,10 @@ struct Args {
 }
 
 fn parse_path_with_position(argument_str: &str) -> Result<String, std::io::Error> {
-    let path_like = PathLikeWithPosition::parse_str::<Infallible>(argument_str, |_, path_str| {
-        Ok(Path::new(path_str).to_path_buf())
-    })
-    .unwrap();
+    let path = PathWithPosition::parse_str(argument_str);
     let curdir = env::current_dir()?;
 
-    let canonicalized = path_like.map_path_like(|path| match fs::canonicalize(&path) {
+    let canonicalized = path.map_path(|path| match fs::canonicalize(&path) {
         Ok(path) => Ok(path),
         Err(e) => {
             if let Some(mut parent) = path.parent() {