Implement Iin vs Vin scan in pbv2_tester and other small things

• Make an AMAC::init() function to centralize the AMAC initial settings
• Add KeithleyMode option to Keithley24XX::sense() to ensure the right value is read
• Run the full pbv2_tester even if LV_ENABLE does not work. It just skips the DCDC efficiency test
• Add the Iin vs Vin scan
• Add HV reading from PS to HV leakage current test.
• Add missing FindLibFTDI1.cmake from #4 (closed). Updated variable names to be compatible with cmake module found in more recent releases of libftdi1.