Running DSP tests which contain xtensa assembly code

[Barabas5532]

To test the ESP32 implementation of abstract_dsp we need to run tests on the ESP32. Some of the functions are implemented using xtensa assembly language for optimal performance.

• ESP-IDF provides a Unity based unit testing framework
• Googletest can run on PlatformIO Issue #1659: Add Support for PlatformIO and Arduino google/googletest#2000
• ESP-DSP offers ANSI C implementation of most (all?) functions. These could be used to test classes that just wrap esp-dsp on Linux. For any custom assembly functions it would make sense to follow the ESP-DSP template and provide a reference implementation in C to compare the assembly output against.
• Simulators