scripts: west: runners: stm32cubeprogrammer: add start address argument

Add new '--start-address' argument to the STM32CubeProgrammer west runner.
This argument can be used to specify an address from which the MCU should
start executing, instead of relying on the default value in CubeProgrammer.

Also update STM32CubeProgrammer runner tests to support new argument.

Signed-off-by: Mathieu Choplain <mathieu.choplain@st.com>