Use the stable rust compiler on windows

[LucioFranco]

Problem

Currently, we require the nightly rust compiler to compile vector on windows due to the need of the windows_by_handle feature rust-lang/rust#63010. This is our only blocker for using the stable compiler on window.

Proposal

The windows_by_handle feature is only a couple of lines implemented in libstd and its is only a nightly feature to ensure the code can be stabilized into libstd. Because we don't have the same requirements we should vendor this code into vector in its own crate in the lib directory. Doing this will allow us to use the stable compiler.

cc @a-rodin

[Hoverbear]

Looks like the only use in Vector is: https://github.com/timberio/vector/blob/b290ceb2aee4242834d434a4bd092fe2a0cece3b/lib/file-source/src/metadata_ext.rs#L23-L30.

Is it better expand this module's code, or create a new module which file-source should depend on?

[LucioFranco]

@Hoverbear what ever you think is easiest :)