Add lowering from AST to logical plan for graph MATCH

[jpschorr]

Note: this is a recapitulation of #551, as that got merged to the wrong branch

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This PR:

• Builds on Add support for GPML-style graph query parsing #548 and Add GPML logical plan and plan -> evaluator. #549
• enables the experimental conformance tests which include the GPML tests
• Refactors some types and traits into non-pub modules.
• Fixes some minor graph evaluation edge case bugs
• Adds lowering from the AST to the logical plan for graph match stuff.

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Some of the graph conformance tests are still failing; These are largely tests that specify only an edge and have implicit start and end nodes (e.g., ( graph MATCH -> )).

The current grammar cannot parse such a construction. I intend to tackle this in follow-up work, perhaps including modernizing the grammar to follow SQL '23.

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

[codecov]

Codecov Report

Attention: Patch coverage is 84.10596% with 48 lines in your changes missing coverage. Please review.

Project coverage is 81.93%. Comparing base (a6d8e0f) to head (12eab14).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
partiql-logical-planner/src/graph.rs	80.09%	34 Missing and 9 partials ⚠️
partiql-logical-planner/src/lower.rs	75.00%	3 Missing and 1 partial ⚠️
partiql-eval/src/plan.rs	96.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #553      +/-   ##
==========================================
+ Coverage   81.56%   81.93%   +0.36%     
==========================================
  Files         107      108       +1     
  Lines       22487    22721     +234     
  Branches    22487    22721     +234     
==========================================
+ Hits        18342    18616     +274     
+ Misses       3632     3567      -65     
- Partials      513      538      +25     

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[github-actions]

Conformance comparison report

	Base (a6d8e0f)	0291c1d	+/-
% Passing	87.15%	86.85%	-0.31%
✅ Passing	5603	5731	128
❌ Failing	826	868	42
🔶 Ignored	0	0	0
Total Tests	6429	6599	170

Number passing in both: 5603

Number failing in both: 826

Number passing in Base (a6d8e0f) but now fail: 0

Number failing in Base (a6d8e0f) but now pass: 0