Add Windows application manifest to rustc-main
Windows allows setting some runtime options using a manifest file. The format of the XML file is documented here: https://docs.microsoft.com/en-us/windows/win32/sbscs/application-manifests
The manifest file in this PR does three things:
* Declares which Windows versions we support. This may help avoid unnecessary compatibility shims.
* Uses the UTF-8 code page. While Rust itself uses UTF-16 APIs, other code may rely on the code page.
* Makes the application long path aware (if also enabled by the user). This allows for the current directory to be longer than `PATH_MAX`.
These changes only affect the `rustc` process and not any other DLLs or compiled programs.
Since RFC 3052 soft deprecated the authors field anyway, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information, we should remove it from
crates in this repo.
