Implement a single testnet function in cardano-testnet

[Jimbo4350]

Currently we have four testnet functions in cardano-testnet. We should have a single testnet function defined as follows:

testnet :: TestnetOptions era -> H.Conf -> Integration TestnetRuntime

Where TestNetOptions era is defined as follows:

data TestnetOptions 
  =  ShelleyOnlyTestnetOptions ShelleyTestnetOptions  
  |  BabbageOnlyTestnetOptions BabbageTestnetOptions   
  |  CardanoTestnetOptions CardanoTestnetOptions

We can convert the current multiple definitions of TestnetOptions as is to the relevant ($era)TestnetOptions via renaming

For simplicity we will not include a Byron era data constructor because it is unlikely users will want to spin up a Byron testnet

[MarcFontaine]

#4544