Support nested query expressions

[j6k4m8]

Allows scalar and relationship expressions to compose inside aggregations and comparisons, including aliases and aggregate ordering.

Example:

MATCH (n)
RETURN n.group, AVG(size(n.name)) AS average
ORDER BY AVG(size(n.name)) DESC

[codspeed]

Merging this PR will not alter performance

✅ 99 untouched benchmarks
🆕 4 new benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	test_benchmark_grouped_collect	N/A	39.6 ms	N/A
🆕	test_benchmark_nested_scalar_aggregation	N/A	41.7 ms	N/A
🆕	test_benchmark_relationship_list_predicate	N/A	68.1 ms	N/A
🆕	test_benchmark_nested_scalar_filtering	N/A	32.3 ms	N/A

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_{Comparing nested-expressions (03f3c81) with master (0738dee)}