Behavior-preserving refactor of Value into a module.

[jpschorr]

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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 84.14873% with 81 lines in your changes missing coverage. Please review.

Project coverage is 80.86%. Comparing base (3f9d17f) to head (0b8a169).
Report is 2 commits behind head on dev-ion-doc.

Files with missing lines	Patch %	Lines
partiql-value/src/value.rs	66.66%	29 Missing and 1 partial ⚠️
partiql-value/src/value/math.rs	79.02%	30 Missing ⚠️
partiql-value/src/value/iter.rs	76.66%	7 Missing ⚠️
partiql-value/src/util.rs	76.19%	5 Missing ⚠️
partiql-parser/src/lexer/mod.rs	90.24%	3 Missing and 1 partial ⚠️
partiql-parser/src/lexer/partiql.rs	90.00%	2 Missing ⚠️
...sion/partiql-extension-visualize/src/ast_to_dot.rs	0.00%	1 Missing ⚠️
partiql-value/src/lib.rs	88.88%	1 Missing ⚠️
partiql-value/src/value/logic.rs	96.66%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           dev-ion-doc     #509      +/-   ##
===============================================
+ Coverage        80.84%   80.86%   +0.01%     
===============================================
  Files               80       86       +6     
  Lines            19398    19402       +4     
  Branches         19398    19402       +4     
===============================================
+ Hits             15683    15690       +7     
- Misses            3291     3293       +2     
+ Partials           424      419       -5     

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[github-actions]

Conformance comparison report

	Base (b1c975d)	3665330	+/-
% Passing	90.37%	90.37%	0.00%
✅ Passing	5732	5732	0
❌ Failing	611	611	0
🔶 Ignored	0	0	0
Total Tests	6343	6343	0

Number passing in both: 5732

Number failing in both: 611

Number passing in Base (b1c975d) but now fail: 0

Number failing in Base (b1c975d) but now pass: 0