Rollup merge of #134996 - bdbai:uwp-support, r=jieyouxu,ChrisDenton

Add UWP (msvc) target support page

- Added Platform Support page for `x86_64-uwp-windows-msvc`, `i686-uwp-windows-msvc`, `thumbv7a-uwp-windows-msvc` and `aarch64-uwp-windows-msvc`
  - Adding myself as a maintainer
  - Removing the ticks for `thumbv7a-pc-windows-msvc` and `thumbv7a-uwp-windows-msvc` as they do not currently build due to #134565 and https://github.com/rust-lang/backtrace-rs/pull/685
- Fixed a few minor issues to let most of the UWP targets compile
- Happy new year to all!

r? jieyouxu

library/std/src/sys/pal/windows/os.rs

@@ -5,8 +5,9 @@
 #[cfg(test)]
 mod tests;
 
-use super::api::{self, WinError};
-use super::to_u16s;
+#[cfg(not(target_vendor = "uwp"))]
+use super::api::WinError;
+use super::{api, to_u16s};
 use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::os::windows::ffi::EncodeWide;