* minor cleanup and rename
* Adds an empty NetworkParameters struct to Network::Testnet variant, updates production code.
* Updates tests
* Adds `NetworkKind` and uses it instead of `Network` in `HistoryTreeParts` and `transparent::Address`
* Adds a [network.testnet_parameters] section to the config, uses `NetworkKind` as zebra_network::Config::network field type, and converts 'Network' to `NetworkKind` before serializing
* Applies some suggestions from code review
* Applies suggestions from code review
* returns b58 prefix constants directly to remove From<NetworkKind> impl for zcash_primitives::consensus::Network
* Applies more suggestions from code review.
* moves conversions to zcash_primitives::consensus::Network to where they're used.
* Apply suggestions from code review
Co-authored-by: Marek <mail@marek.onl>
* rename `network` variables and method names typed as NetworkKind to `network_kind`
* use only test block heights for the network associated with them
* Applies more suggestions from code review.
* Rename `NetworkParameters` to `Parameters` and move it a new `testnet` module
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Co-authored-by: Marek <mail@marek.onl>