Add allow all wildcard for allowed clients

[colin-axner]

Summary

Add a wildcard to allow all client types. Traditionally we use "*". This would allow any wired up light client modules to be allowed by default. Governance could then override with a well formed list if it wants to exclude certain light client types.

Originally the AllowedClients list was to add a enable button for certain clients. Core IBC shipped with tendermint, solomachine and localhost but only tendermint was fully functional at launch which made it useful to allow the other types to be enabled over time. Later on we began to use this param to disable client types in security conscious situations. Given this later usage, it would have been more functional to add a DisallowedClients param, but so goes history

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