create-testnet-data: various enhancements

[smelc]

Changelog

- description: |
    Improvements to --create-testnet-data
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - improvement    # QoL changes e.g. refactoring
  # - bugfix         # fixes a defect
  - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

This PR improves on a number of things, in particuler to make the user experience better (thinking of QA that will use this soon):

• create-testnet-data: add --drep-keys flag #565 had forgotten to generate the README.md file in the folder of DRep keys. This PR does that.
• The documentation for --supply and --supply-delegated is made more explicit, something requested many times by @CarlosLopezDeLara Will be done differently in another PR in the end
• Tests of create-tesnet-data are augmented a bit

Fixes #492

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[Jimbo4350]

One comment

[Jimbo4350]

This is confusing behaviour. --supply-delegated shouldn't add to the total supply it should delegate a proportion (or all) of whatever was specified by --supply. We should modify this behaviour in create-testnet-data.

[smelc]

Let me do that in another PR 👍 So removing the change to the help from this PR.

[smelc]

-> https://github.com/IntersectMBO/cardano-cli/commits/smelc/create-testnet-data-rework-supply-arguments/

[smelc]

PRed: #581