Auto merge of #1501 - samrat:fix-fs-error-handling, r=RalfJung
Auto merge of #1501 - samrat:fix-fs-error-handling, r=RalfJung

Bubble up errors from FileDescriptor::as_file_handle

Instead of indicating incorrectly that a handle was not found, return the error from `as_file_handle` indicating the operation is not supported on the FD.

Addresses some comments in #1495

rust-lang/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri