Plugin API - deprecate methods returning optional RPC host/port

[macfarla]

In BesuConfiguration methods getRpcHttpHost and getRpcHttpPort (which return Optionals) have been deprecated in favour of getConfiguredRpcHttpHost and getConfiguredRpcHttpPort which return the actual values, which will always be populated since these options have defaults.

Not having to deal unnecessarily with Optionals makes life slightly easier in the plugins.

PR description

Fixed Issue(s)

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