[DRAFT] Removes PartiQLValue from the planner

[RCHowell]

Relevant Issues

• [V1] Remove PartiQLValue from the AST #1589
• Generalizes back-tick Ion to a variant pair in the AST #1591
• https://github.com/orgs/partiql/discussions/92

Description

This PR removes PartiQLValue from the planner in favor of Datum – however the build is currently broken due to plan equivalence testing which I believe is the result of not having a equals defined for Datum.

I think we will need to change the wording of this because we need to check IR equivalence, no necessarily evaluation. Or perhaps the plan comparator can be a bit more clever...

The conventional use
* of {@link java.util.HashMap}, {@link java.util.HashSet}, {@link Object#hashCode()}, and
* {@link Object#equals(Object)} will not work outright with Datum to implement the before-mentioned operations due
* to requirements by the PartiQL and SQL Specifications.

Other Information

• Updated Unreleased Section in CHANGELOG: NO
• Any backward-incompatible changes? NO
• Any new external dependencies? NO
• Do your changes comply with the Contributing Guidelines
  and Code Style Guidelines? YES

License Information

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.