~ruther/vhdl-spi-2

ref: 19cab4548832988e5a3dd440796c69617c46e2f6 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