FPP CMake integration

[tiffany1618]

Change Description

• Add parameterGENERATED_SOURCES, a list of sources generated by previous autocoders, to the _filter_sources function in cmake/autocoder/autocoder.cmake
• Change the ai_xml_is_supported function in cmake/autocoder/ai_xml.cmake to also filter sources against previously generated sources. This means that XML autocoder will only receive Ai.xml files whose corresponding Ac.cpp and Ac.hpp files have not already been generated by the FPP autocoder, preventing it from overwriting those files.

Rationale

This change is necessary to support FPP v1.1.0, which will include C++ code generation for FPP enums, arrays, and structs, intended to replace the XML autocoder's C++ code generation for enums, arrays, and structs.

[LeStarch]

This looks good to me. I'd like to test cmake 3.13, and see what happens.

[LeStarch]

This code works as expected in CMake 3.21+, but breaks on CMake 3.13-3.16. The reason is that the code that replicates the cmake_language CALL functionality supports a maximum number of arguments.

An easy fix should be to switch from ARGN to ARG2 and pass GENERATED_FILES as a list rather than unrolling it. I'll go ahead and try this fix.

[LeStarch]

The changes worked, so I pushed a commit to this branch. Once CI is done I will merge!