Move timeout properties to Socket and IO::FileDescriptor

[straight-shoota]

Both Socket and IO::FileDescriptor have public read_timeout and write_timeout properties. For some reasons these ended up being defined in IO::Evented (which is a shared module between the two, but only on Unix systems), and IO::Overlapped (same job, but on Windows). That puts a general public API in places that are implementation-specific. The definitions are exactly identical, but they should never be duplicated in platform specific modules. They need to be defined in the public API space.

This patch moves the definitions to Socket and IO::FileDescriptor directly. This ends up still duplicated, but that's okay. Both types don't have any common ancestors except generic IO. It's just coincidental that the internal implementation is shared.

The code can also be simplified a by defining getters and setters with the property macro. That reduces the code a lot and leaves only the odd Number overloads (which might be good for deprecation? cf. #14368) preventing it from becoming a two-liner.