Add Parsing of EXCLUDE

[jpschorr]

For the EXCLUDE clause, implements:

• AST nodes
• parsing,
• pretty-printing

Cf. partiql/partiql-docs#51

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[codecov]

Codecov Report

Attention: Patch coverage is 61.42857% with 27 lines in your changes missing coverage. Please review.

Project coverage is 80.98%. Comparing base (3ca67b7) to head (df946e4).

Files	Patch %	Lines
partiql-ast/src/visit.rs	0.00%	18 Missing ⚠️
partiql-ast/src/ast.rs	0.00%	6 Missing ⚠️
partiql-logical-planner/src/lower.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #480      +/-   ##
==========================================
- Coverage   81.05%   80.98%   -0.08%     
==========================================
  Files          68       68              
  Lines       18608    18680      +72     
  Branches    18608    18680      +72     
==========================================
+ Hits        15083    15128      +45     
- Misses       3082     3109      +27     
  Partials      443      443              

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[github-actions]

Conformance comparison report

	Base (3ca67b7)	c583676	+/-
% Passing	90.35%	90.35%	0.00%
✅ Passing	5731	5731	0
❌ Failing	612	612	0
🔶 Ignored	0	0	0
Total Tests	6343	6343	0

Number passing in both: 5731

Number failing in both: 612

Number passing in Base (3ca67b7) but now fail: 0

Number failing in Base (3ca67b7) but now pass: 0

[alancai98]

I like that the naming of the enum variants are the same as PathStep