added wasm light client

[sampocs]

Context

Added wasm light client to integrate with union bridge.

Referenced the following during the integration:

• Wasm client integration guide Wasm client integration guide
• Integrating light clients guide
• Osmosis integration

Open Questions

• The compatibility matrix doesn't list ibc v7.4 - I used commit 7ee2a2452b79d0bc8316dc622a1243afa058e8cb which is for v7.3
• The client router is not in ibc v7 so I excluded the following lines from app.go

 clientRouter := app.IBCKeeper.ClientKeeper.GetRouter()
 wasmLightClientModule := wasm.NewLightClientModule(app.WasmClientKeeper)
 clientRouter.AddRoute(ibcwasmtypes.ModuleName, &wasmLightClientModule)

Brief Changelog

• Added wasm client, sharing the same wasmVM as x/wasm
• Added the store key
• Added the client name to AllowedClients in the upgrade handler

[assafmo]

Left a few comments, overall LGTM.