~ruther/vhdl-spi-2

ref: 5c7a8bb412b0f4dc78f9b891819452e477869678 vhdl-spi-2/hdl_spi/tests d---------
feat: tests for multiple transmissions, rx lost
chore: add ghdl support vhdl2008 arg
feat: add first basic test
chore: few updates
feat: implement initial hdl_spi