v2.4.0

ENH: adding fx2_to_bus.v interface for MIO (FX2) slow bus
MIO only: use the fx2_to_bus interface to fix read errors on the FX2 slow bus
BUG: fix GPIO driver register definition
BUG: possible lost of data in sram_fifo
ENH: update mio examples and add CI tests
ENH: new sram test example
ENH: add delay and trigger mode for gpac_adc_rx
ENH: more simulation models (e.g. DCM)
ENH: keithley_6517a driver