Remove support for MinGW on Windows

[skhamis]

In an effort to simplify our NSS issues: #5210

Application services has supported building NSS via MinGW for Windows due to a when our CI started failing due to a change from rust which broke .lib linked libs

The change from static .lib for windows occurred in this PR: #3210

It looks like this is no longer an issue in the latest versions of rust:

• Windows: Static libraries can't be linked as files by libtool/MinGW due to .lib extension rust-lang/rust#69904
• Windows: Static libraries should end with .lib not .a when using the MSVC ABI install rust-lang/rust#29508
• Fix staticlib name for *-pc-windows-gnu targets rust-lang/rust#70937

From what I understand, it officially works for both *-windows-gnu and MSVC targets now. However, since the official NSS CI builds for MSVC targets.
Dropping support for *-windows-gnu allows us:

• To not have to support updating *-windows-gnu via complicated phab patch for potentially no consumers.
• Keeps us inline with the artifact binaries produced by NSS CI, which also can simplify our update process

Open to questions, concerns or issues with dropping support!

┆Issue is synchronized with this Jira Task
┆Sprint End Date: 2022-11-25