PLT-776 Modified the Utxo indexer property test for testing provided target addresses

[koslambrou]

• Changed the genUtxoEvent generator so that I can also return the tx that was used to generate it

• The generated tx is customized, thus the modified property test is now a lot faster (runs under 1s)

• Fixed a bug in the datum extraction in the Utxo indexer

Pre-submit checklist:

• Branch
  • [x] Tests are provided (if possible)
  • [x] Commit sequence broadly makes sense
  • [x] Key commits have useful messages
  • [x] Formatting, PNG optimization, etc. are updated
  • [x] Important changes are reflected in changelog.d of the affected packages
• PR
  • [ ] Self-reviewed the diff
  • [x] Useful pull request description
  • [ ] Reference the ADR in the PR and reference the PR in the ADR (if revelant)
  • [x] Reviewer requested

[koslambrou]

@kayvank Following your remark, I refactored quite a bit the module in question and created a Mockchain module for generating transactions. Therefore, I'll re-request a review from you :)

Also, the TxOutBalance datatype in the test-lib might be useful for you in your refactoring of the UtxoEvent.

[koslambrou]

@eyeinsky Ping for review