Add a configuration to ignore packets with memo or receiver fields too big

[ljoss17]

Summary

Some ICS20 packets might have very big memo and/or receiver fields which could cause issues. IBC-GO v8 introduces a maximum limit for these fields: https://github.com/cosmos/ibc-go/blob/04e14a7079e18323c64d4e00e12cf77708d24701/modules/apps/transfer/types/msgs.go#L15.

Hermes should be able to configure a limit used to filter packets depending on the size of the memo and receiver fields.

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