win: lazy-load [GS]etThreadDescription symbols

[bnoordhuis]

As said symbols are unavailable on Windows Server 2016.

Fixes: #4677

[bnoordhuis]

Not sure why that breaks Windows Server 2019 and 2022... anyone have ideas? The thread name test now fails with UV_ENOSYS so apparently libuv is not finding the symbols.

[santigimeno]

The actual test doesn't need to use a uv_loop_t instance so uv_loop_init() is never called, so uv__winapi_init() isn't either. Maybe move the new code to a separate function which is called uv_once() from the new thread name methods?

[bnoordhuis]

The actual test doesn't need to use a uv_loop_t instance so uv_loop_init() is never called, so uv__winapi_init() isn't either. Maybe move the new code to a separate function which is called uv_once() from the new thread name methods?

Oh, that's such a footgun... but yeah, I missed that. Thanks!