Refactor: expression parsing refactor to support nested aggregations

[snork-alt]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 4050903288

• 950 of 1352 (70.27%) changed or added relevant lines in 16 files are covered.
• 501 unchanged lines in 16 files lost coverage.
• Overall coverage increased (+0.1%) to 65.71%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dozer-sql/src/pipeline/aggregation/factory.rs	10	11	90.91%
dozer-types/src/tests/field_serialize_test.rs	2	3	66.67%
dozer-sql/src/pipeline/aggregation/aggregator.rs	0	9	0.0%
dozer-sql/src/pipeline/planner/projection.rs	108	117	92.31%
dozer-sql/src/pipeline/expression/scalar/string.rs	1	11	9.09%
dozer-sql/src/pipeline/expression/tests/builer_new_test.rs	470	480	97.92%
dozer-sql/src/pipeline/product/factory.rs	25	44	56.82%
dozer-sql/src/pipeline/expression/operator.rs	0	26	0.0%
dozer-sql/src/pipeline/expression/builder.rs	43	91	47.25%
dozer-sql/src/pipeline/expression/execution.rs	40	102	39.22%

Files with Coverage Reduction	New Missed Lines	%
dozer-sql/src/pipeline/expression/cast.rs	1	49.5%
dozer-sql/src/pipeline/aggregation/sum.rs	4	64.71%
dozer-sql/src/pipeline/errors.rs	4	33.33%
dozer-sql/src/pipeline/expression/scalar/common.rs	5	73.13%
dozer-sql/src/pipeline/expression/operator.rs	10	36.11%
dozer-sql/src/pipeline/builder.rs	12	74.1%
dozer-sql/src/pipeline/expression/scalar/string.rs	12	70.2%
dozer-sql/src/pipeline/aggregation/aggregator.rs	15	60.67%
dozer-sql/src/pipeline/product/factory.rs	16	57.32%
dozer-sql/src/pipeline/expression/execution.rs	18	26.84%

Totals
Change from base Build 4050483351:	0.1%
Covered Lines:	24538
Relevant Lines:	37343

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💛 - Coveralls