Move non-required modules to BI_HDL_Cores

When we move the boot ROM functionality from the System to the Application I would propose to move BootRomWbMaster.sv to BI_HDL_Cores.

This also raises the question about these two modules:

• DS18B20Emu.sv
• SfpIdReader.sv

Neither is required for the System, but only for applications using White Rabbit support (for example the BTrain Receiver).

I would propose to also move these.