Remove MSVC shim header cruft, reduce CMake overhead

[marcusmueller]

closes #1680, closes #1674

[ryanvolz]

This looks good to my eye, with the caveat that additionally you'll need to remove add_definitions(-DHAVE_CONFIG_H) from CMakeLists.txt to get it compiling! A conda build using these changes compiles successfully with MSVC (and on Linux and macOS).

[marcusmueller]

I've removed the CMake Check cleanup, which is a separate issue (and now in #4256), and added in -DHAVE_CONFIG_H

[mbr0wn]

Introduces new warnings:

/__w/gnuradio/gnuradio/gr-blocks/lib/udp_sink_impl.cc: In member function 'virtual int gr::blocks::udp_sink_impl::work(int, gr_vector_const_void_star&, gr_vector_void_star&)':
/__w/gnuradio/gnuradio/gr-blocks/lib/udp_sink_impl.cc:110:23: error: comparison of integer expressions of different signedness: 'std::ptrdiff_t' {aka 'long int'} and 'const size_t' {aka 'const long unsigned int'} [-Werror=sign-compare]
  110 |     while (bytes_sent < total_size) {
      |            ~~~~~~~~~~~^~~~~~~~~~~~
/__w/gnuradio/gnuradio/gr-blocks/lib/udp_sink_impl.cc:111:23: error: operation on 'bytes_to_send' may be undefined [-Werror=sequence-point]
  111 |         bytes_to_send = bytes_to_send =
      |         ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  112 |             std::min(static_cast<std::ptrdiff_t>(d_payload_size),
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  113 |                      static_cast<std::ptrdiff_t>(total_size - bytes_sent));
      |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[ 36%] Building CXX object gr-zeromq/python/zeromq/bindings/CMakeFiles/zeromq_python.dir/pull_msg_source_python.cc.o
cc1plus: all warnings being treated as errors

[mbr0wn]

Can you please fix the compiler warnings -- we no do -Werror where applicable.

[mbr0wn]

Maybe merge the fixup UDP commit with the first one?

[mbr0wn]

Merged manually + squashed.