Proposed changes to split tests into separate binaries for efr32 [Version 2]

[feasel0]

REPLACED BY: 34769

The approach here is to move the silabs_executable target into chip_test_suite. The advantage is that we don't need to update anything if we add a new directory of tests, since it will add new efr32 binary targets each time chip_test_suite gets invoked. The disadvantage is that it moves a lot of efr32-specific stuff into chip_test_suite, which may not be desirable.

This version creates a binary for each test source (e.g. src/messaging/tests/TestExchange.cpp). It can easily be modified to create a binary for each suite (e.g. src/messaging/tests) just by moving the location of the silabs_executable target outside of the foreach(_test, invoker.test_sources) loop and making a few other minor changes. However in the interest of allowing for very large tests or for test directories with many test sources in them, I decided to split it per test source.

So far I have not gotten this to build successfully, probably due to nl_test_service being defined in the wrong place. Solving this issue is the next step, however I wanted to stop and get some feedback about the overall approach before going further.

(This is a work in progress, so please ignore any commented-out code and print statements.)

[feasel0]

A bunch of stuff needs importing into here since it is used by silabs_executable. Eventually I'll find a cleaner way to do this.

[feasel0]

The "copy" action only needs to be done once per build, however now that silabs_executable is being called many times it ends up trying to copy these same python files repeatedly which causes an error. I could not find a clean way of making it only copy once, so as a temporary fix I changed the names of the files to be something unique. However ultimately this is not what we want, so I'll need to circle back and fix this properly.

[feasel0]

The chip_test_suite template makes calls to pw_test (part of pigweed) for each test source instead of calling chip_test (part of our codebase). Currently chip_test is only being used by chip_test_suite_using_nltest, so I presume it has not been updated to work with PW unit testing. If chip_test were updated to support PW, we could make it so that chip_test_suite calls chip_test (instead of pw_test), and then I could probably move all of the silabs_executable stuff and the efr32 stuff into chip_test rather than the foreach loop of chip_test_suite, which would be slightly cleaner.