missing size validations in lightclient and connection creation

[yihuang]

Summary of Bug

light client and connection creation is permissionless, we should limit the field lengths of user input to mitigate storage spam.

• The merkle root hash size in ConsensusState.
• counterparty prefix size in ConnectionInit msg.

Expected Behaviour

Version

Steps to Reproduce

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned
• Estimate provided

[linear]

IBCGO-2387