Introduce basic T2 topology (#2638)

* Definition of Basic T2 topology

3 line card topology with all ports connected to VM

* T2 topology file

Adding T2 topology file for a SONiC Chassis that has 4 DUT's:
  - 3 linecards - dut_index 0, 1, and 2
  - 1 supervisor card - dut_index 3

Each linecard has 24 VM's.

BGP info:
   DUT ASN: 65100
  Linecard 1 (dut_index 0) has 24 eBGP peers, each with the same ASN 65200
  Linecard 2 (dut_index 1) has 24 eBGP peers, each with a different ASN (65001-65023)
  Linecard 3 (dut_index 2) has 24 eBGP peers, each with a different ASN (65024-65047)

Co-authored-by: sanmalho-git <66454160+sanmalho-git@users.noreply.github.com>