Separate EvmApp interface per test

[cloudgray]

The current EvmApp interface requires getters for all keepers used by evmd.

However, most external apps injected into the tests do not use all of these keepers.

For example, an external app might not use the IBC Keeper, yet the EvmApp interface forces the implementation of a GetIBCKeeper() method. This requirement exists only because the IBC tests use the IBC Keeper — meaning that chains not using IBC should not have to implement this interface.

Therefore, we need to define and use separate EvmApp interfaces per test, depending on which keepers are actually required.

[linear]

EVM-385