Ledger types testing

[aleeusgr]

This is an experiment, it consists of two parts:

• upstreaming Arbitrary instances from plutarch to plutus-ledger-api
• asserting the value of proposition "all types exported by plutus ledger api provide arbitraries".

Pre-submit checklist:

• Branch
  • Tests are provided (if possible)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
  • Changelog fragments have been written (if appropriate)
  • Relevant tickets are mentioned in commit messages
  • Formatting, PNG optimization, etc. are updated
• PR
  • (For external contributions) Corresponding issue exists and is linked in the description QuickCheck Arbitrary instances for Ledger types #6210
  • Targeting master unless this is a cherry-pick backport
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested

[aleeusgr]

I get errors:

No instance for ‘Arbitrary DatumHash’                                                                            
        arising from a use of ‘arbitrary’
...
No instance for ‘Arbitrary Datum’                                                                            
        arising from a use of ‘arbitrary’