feat: tests for multiple transmissions, rx lost

chore: add ghdl support vhdl2008 arg

chore: update cocotb

fix: sck generation

Sampling and changing was offset by one clock,
which is unnecesary. The clock wasn't correct
frequency, ie. divisor 2 led to division by 3

fix: master_ctrl_rst_n shou be used, not master_ctrl_rst, start_clock is split

fix: do not pass rx_serial_o from spi_multiplexor when not enabled

fix: prevent slave ctrl sending X's

feat: add first basic test

chore: few updates

feat: implement masterslave spi switch peripheral

feat: implement initial hdl_spi