feat: add windows_named_pipe() option to client builder

[seanmonstar]

Similar to adding support for Unix Domain Sockets in #2624, this adds support for Windows Named Pipes that functions the same way.

cc @danielsn @morrisonlevi

[danielsn]

Looks good to me.

[danielsn]

On DataDog/libdatadog#1412

I got an error in CI when I tried to use this. Is this correct? Is there a reason unix accepts a path-buf but windows doesn't?

error[E0277]: the trait bound `std::path::PathBuf: reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider` is not satisfied
    --> libdd-profiling\src\exporter\profile_exporter.rs:89:54
     |
  89 |                 builder = builder.windows_named_pipe(pipe_path);
     |                                   ------------------ ^^^^^^^^^ the trait `reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider` is not implemented for `std::path::PathBuf`
     |                                   |
     |                                   required by a bound introduced by this call
     |
     = help: the following other types implement trait `reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider`:
               &str
               std::string::String
note: required by a bound in `reqwest::ClientBuilder::windows_named_pipe`
    --> C:\Users\runneradmin\.cargo\git\checkouts\reqwest-691f072c9d01bc8f\272b6c9\src\async_impl\client.rs:1814:52
     |
1814 |     pub fn windows_named_pipe(mut self, pipe: impl WindowsNamedPipeProvider) -> ClientBuilder {
     |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `ClientBuilder::windows_named_pipe`

error[E0277]: the trait bound `std::path::PathBuf: reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider` is not satisfied
    --> libdd-profiling\src\exporter\profile_exporter.rs:111:54
     |
 111 |                 builder = builder.windows_named_pipe(pipe_path);
     |                                   ------------------ ^^^^^^^^^ the trait `reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider` is not implemented for `std::path::PathBuf`
     |                                   |
     |                                   required by a bound introduced by this call
     |
     = help: the following other types implement trait `reqwest::connect::windows_named_pipe::WindowsNamedPipeProvider`:
               &str
               std::string::String
note: required by a bound in `reqwest::ClientBuilder::windows_named_pipe`
    --> C:\Users\runneradmin\.cargo\git\checkouts\reqwest-691f072c9d01bc8f\272b6c9\src\async_impl\client.rs:1814:52
     |
1814 |     pub fn windows_named_pipe(mut self, pipe: impl WindowsNamedPipeProvider) -> ClientBuilder {
     |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `ClientBuilder::windows_named_pipe`

[seanmonstar]

Seems like an oversight. Windows named pipes want an OsStr, but I see there's an AsRef<OsStr> for PathBuf. So I can add in a couple more impls inside reqwest.

[danielsn]

Looks like this passes when we try to us it DataDog/libdatadog#1412. Thanks!