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.

Use stop toggling instead of severity failure to stop simulation, because otherwise the tb cannot be used as component in a multi-tb.

Default eth_ram_mosi <= c_mem_mosi_rst to avoid sim warnings. Adde tb_end to be able to use run -all.

- Use common_network_layers_pkg from common (was eth_layers in $UNB)
- Use tech_tse_pkg and tb_tech_tse_pkg from tech_tse_lib (was work=tse_lib in $UNB)