eos_designs: add more RD/RT override options under SVIs / l2vlans

[ClausHolbechArista]

Enhancement summary

Add support for setting

rt_admin_override
rd_override
rd_admin_override

under each svi/l2vlan.

Which component of AVD is impacted

eos_designs

Use case example

.

Describe the solution you would like

.

Describe alternatives you have considered

No response

Additional context

No response

Contributing Guide

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[ClausHolbechArista]

Maybe also consider allowing vlan as assigned number for rt/rd (set using global overlay_rt_type and overlay_rd_type)