Add datum helpers to plutus-ledger-api and plutus-tx

[awkure]

This PR is a part of https://github.com/input-output-hk/plutus/pull/3852 that adds helpers for working with datums in plutus-tx and plutus-ledger-api

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• Branch
  • [X] Tests are provided (if possible)
  • [X] Commit sequence broadly makes sense
  • [X] Key commits have useful messages
  • [X] Relevant tickets are mentioned in commit messages
  • [X] Formatting, materialized Nix files, PNG optimization, etc. are updated
• PR
  • [ ] Self-reviewed the diff
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