Charge injection and internal threshold scan

This PR implements a first version of working charge injection. The secret sauce is to set etroc.wr_reg("chargeInjectionDelay", 0xa). The routing that runs the delay scans also uses the newly implemented internal threshold scan. In order to get some quick results, run ipython3 -i test_ETROC.py -- --test_chip --partial --module 1 --hard_reset --mode dual --skip_sanity_checks --qinj.

This will run the internal threshold scan (using the ACC register) for pixel (1,1) and then perform a Qinj-to-L1A delay scan between 500 and 510 clock cycles. This window should be sufficiently large for the current test setups with the default ETROC parameters.