[#895] Add getAliasMaybe to morley-client

Description

Just like we have resolveAddressMaybe and resolveAddress, we should also have getAliasMaybe and getAlias.

• HasTezosClient now exposes as getAliasEither which returns a Left KindedAddress kind if the alias could not be resolved
• getAlias has moved from the HasTezosClient class to Morley.Client.TezosClient.Impl module
• getAliasMaybe has been added (in MorleyClient.TezosClient.Class)
• morley-client tests now throw and UnknownAddress exception (like the "real" getAlias) instead UnknownContract

Related issue(s)

Resolves #895 (closed)

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