Miscellaneous fixes and improvements

[x] Fix Rcc::enable for STM32H7 comparator
[x] Add STM32 advanced timer isOutputEnabled()
[x] Suppress GCC ABI nuisance warning ("note: parameter passing for argument of type '...' when C++17 is enabled changed to match C++14 in GCC 10.1")
[x] Fix RTT logger if data structure is not in RAM with lowest address
[x] Allow unit test case names in snake_case (test_foo())
[x] Treat missing return in function as error (this is always undefined behaviour)
[x] Fix compilation of STM32G0 DMA. The CI didn't catch it because the template function is never instantiated in the test suite.
[x] Fix reconfiguring DMAMUX requests
[x] Fix STM32H7 32-bit timer counter size
[x] Fix STM32H7 ADC asynchronous clock
[x] Fix sampling time configuration in STM32F3 ADC driver
[x] Fix compilation of STM32 DMA channel clearInterruptFlags()

modm-io / modm