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/recent_projects/src/dev_servers.rs

@@ -39,7 +39,7 @@ use ui::{
     RadioWithLabel, Tooltip,
 };
 use ui_input::{FieldLabelLayout, TextField};
-use util::paths::PathLikeWithPosition;
+use util::paths::PathWithPosition;
 use util::ResultExt;
 use workspace::notifications::NotifyResultExt;
 use workspace::OpenOptions;
@@ -991,7 +991,7 @@ impl DevServerProjects {
                         project
                             .paths
                             .into_iter()
-                            .map(|path| PathLikeWithPosition::from_path(PathBuf::from(path)))
+                            .map(|path| PathWithPosition::from_path(PathBuf::from(path)))
                             .collect(),
                         app_state,
                         OpenOptions::default(),