cardano-testnet: Split parsers into shared, env-only, and runtime-only

## Problem The current `pCardanoTestnetCliOptions` parser is shared between `create-env` and `cardano` subcommands, parameterised by a `TestnetMode` that only affects the tx-generator flag. This means `create-env` accepts and silently ignores runtime-only flags like `--nodeLoggingFormat` and `--enable-new-epoch-state-logging`. ## Proposed fix After splitting the options records (#6459), split the parser accordingly: - `pSharedOptions` — parses fields used by both phases (nodes, era, supply, dreps) - `pEnvOnlyOptions` — parses fields only for env creation (on-chain params) - `pRuntimeOnlyOptions` — parses fields only for runtime (logging format, epoch state logging, tx-generator) The `create-env` parser combines `pSharedOptions + pEnvOnlyOptions`. The `cardano` parser combines `pSharedOptions + pEnvOnlyOptions + pRuntimeOnlyOptions`. This is ~20 lines of rearranging existing parser combinators in `Parsers/Cardano.hs`. ## Depends on - #6459 (split options records — this is the parser-side companion) ## Type: Refactoring ## Effort: Low (~20 lines) ## Risk: Low