refactor(windows-rs): use "wide" fns uniformly

This commit builds on @EBNull's comment shedding light on the uses of
the -A and -W functions in the Win32 API, and standardizes the calling
of the -W functions across the project.

Since UTF-16 String handling is a bit lacking in the Rust standard
library, I have pulled in the widestring crate to use the
from_slice_truncate fn to automagically remove all of the trailing null
chars when handling values returned from the various Win32 -W fns.

Comment ref: 657ac441ae (r135643553)

Cargo.lock

@@ -827,6 +827,7 @@ dependencies = [
  "tracing-subscriber",
  "uds_windows",
  "which",
+ "widestring",
  "windows",
  "windows-implement",
  "windows-interface",
@@ -2331,6 +2332,12 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "widestring"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "653f141f39ec16bba3c5abe400a0c60da7468261cc2cbf36805022876bc721a8"
+
 [[package]]
 name = "winapi"
 version = "0.2.8"