Fix path_rename_trailing_slashes test case on Win

This commit adds a utility routine
`strip_trailing_slashes_and_concatenate` which is common for
`path_rename` and `path_symlink` on Windows, and checks if the resolved
`PathGet` indeed contains a trailing slash(es) before striping them
off. Secondly, this commit fixes `path_rename_trailing_slashes` test
case by adding two additional checks for potentially erroneous
conditions, and raising `ENOTDIR` if any happens to be true.

build.rs

@@ -198,7 +198,6 @@ mod wasm_tests {
                         "symlink_loop" => true,
                         "truncation_rights" => true,
                         "fd_readdir" => true,
-                        "path_rename_trailing_slashes" => true,
                         "poll_oneoff" => true,
                         _ => false,
                     }