eRPC 1.4.1. updates

-- Added support for unions type non-wrapped by structure.
-- Added callbacks support.
-- Strip ZC from RPMSG Lite file and classes names.
-- Added support @external annotation for functions.
-- Added support @name annotation.
-- Changed @outputDir annotation to @output_dir annotation.
-- Tests from execution section test_others were moved into pytest section.
-- Updated documentation.
-- Added MU transport layer.
-- Added RPMSG Lite RTOS TTY transport layer.
-- Extended threading to support put from interrupts.
-- Improved doxygen comments handling.
-- Added version verification and IDL version verification between eRPC code and eRPC generated shim code.
-- Fixed IDL file examples.

Merge branch 'dev_erpc_1.4' into develop

Updated eRPC to 1.4 version.

-- Updated Copyrights.
-- Formatted code. Added script for proper code formatting.
-- Moved C specific code from SymbolScanner into CGenerator.
-- Have only one client_error_handler_t type defnition.
-- Added and fixed many pytest based tests.
-- Fixed Cygwin build.
-- Fixed linker. For case when for building was used different compiler.
-- Added tests for testing arbitrated transport layer.
-- test_doxygen was moved into test_others. Added test for imports.
-- Fixed doxygen comments parsing.
-- Replaced RPMSG Lite transport with RPMSG Lite ZeroCopy. Improved transport related code to support this transport type.
-- Improved static queue.
-- Usage codecs in setup functions is same as transports.
-- Fixed Uart transport type.
-- Updated documentation and moved into docs.