Zephyr regression tests executed on QEMU

[erlingrj]

This PR enables running parts of the regression test suite on an QEMU-emulation with Zephyr in CI.
To this we have the following changes:

• Add a bash script for compiling and running the emulator and parsing its output and killing the emulator either after a timeout or after the LF program has exited and printed "exit"
• Decouple "TestLevel" from test categories. THis was a change introduced by @arengarajan99, but I don't think it makes sense to say that the GenericTests are bundled with a TestLevel.EXECUTE and ArduinoTests are bundled with TestLevel.BUILD. This change makes the TestLevel and input to the test. This was we can have the buildZephyrGenericTests which configures and builds the GEnericTests for a Zephyr platform.
• To get this to work I need to configure the regression tests for Zephyr by changing the target property. I need to disable tracing and threading (currently) and also set platform to Zephyr. However, the TestBase.java includes a line that reloads the target properties after the Configurator is applied and thus overwrites these changes. I have commented out this line. But I am guessing that this will lead to some other test failures. So we need to find a workaround there.

[erlingrj]

Also fixes this: lf-lang/reactor-c#180 and lf-lang/reactor-c#185