Add support for BTLS on Windows targeting both cygwin/mingw and msvc build runtimes.

• Build BTLS as part of cygwin/mingw build. Build BTLS on Windows, cygwin/mingw. #9306.
• Validate pass on basic BTLS tests using cygwin/mingw build (NOTE, by default CI uses msvc build runtime to run tests). Build BTLS on Windows, cygwin/mingw. #9306.
• Build BTLS as part of msvc build. Build BTLS on Windows, Visual Studio. #11100.
• Do a better integration between autoconf and msvc build. Implement logic to pickup build parameters from autoconf step (in this case BTLS but should be other configs as well) and add logic to build, use and link external repro's as part of msvc build without additional configuration. Build BTLS on Windows, Visual Studio. #11100.
• Add support for assembler BTLS builds on cygwin and msvc builds. Windows BTLS assembler build support (cygwin/msvc). #11234.
• Update Mono Windows build instructions. Add option to integrate msvc build into regular make build. #11343, Refactoring, renewing, upgrading of Windows build instructions. website#411
• Update documentation related to additional build dependencies when build using BTLS. Add option to integrate msvc build into regular make build. #11343, Refactoring, renewing, upgrading of Windows build instructions. website#411