Added tb_tb_tb_eth.vhd to simulate eth for multiple technologies (currently only stratixiv).

No functional change. Noe use constants and functions from common_netork_*_pkg.vhd. tb_tb_tb_eth_regression runs OK.

Renamed eth_layers_pkg package in common/src/vhdl/common_network_layers_pkg.vhd into common_network_layers_pkg.

Only file name change, definition names need to be changed later to have prefix tech_tse_*.