Replace EVM.BridgeRouter interface with resource definition

[sisyphusSmiling]

Issue To Be Solved

The purpose of the BridgeRouter construct was to both decouple the routing of bridge requests from core EVM functionality and enable an extensible pathway for bridge replacements and routing redirects. Currently, this construct is an interface which is implemented in bridge-related contracts; however, when a new set of bridge contracts are deployed, the underlying BridgeRouter type also changes. This presents a problem when redirecting to a new set of bridge contracts as the new contracts cannot be fully decoupled from the old ones - the initial version's router is used to contain any successive BridgeAccessor Capability.

Suggest A Solution

Replace the BridgeRouter interface definition with one of a resource in the EVM contract. Alternatively, the BridgeRouter interface could remain but the implementation and initialization defined in a new contract deployed to the EVM account.

[sisyphusSmiling]

Closing as will be moving forward with contracts as-is