Sorted dict

[amascolo]

Support for sorting and hybrid queries (i.e. using SortedDict and Range). Includes all queries ported over to SDQL.

[amascolo]

Details that came up during implementation:

1. added a Timer expression in SDQL to mark where the timer should start – since we need to exclude the initial data sorting time in benchmarks (nice aside is that now we don't need to treat load expressions as a special case)

2. added external function SortedIndices - to sort the initial data

3. added external function SortedVec - to sort the tries

4. special case to call emplace_back - when constructing @vec { <...> -> 1 } we interpret the relational form <...> -> 1 as i -> <...> and append elements to a std::vec

5. special case to call at - since in SortedDict we can't use [ ] which has special semantics for insertion (this wasn't an issue previously for vecdict since after construction we only iterated on it – i.e. set semantics – whereas here we access elements)

6. cache the last found element – to avoid calling SortedDict::find twice in situations where we check with contains then retrieve the element using at (in handwritten C++ code we could assign the result of find – i.e. an iterator - to some variable, but this isn't representable in SDQL)

[amascolo]

Have ported query FJ 3a to SDQL and checked its performance is identical to handwritten C++.

Codegen and runtime should work everywhere, just need to generate all the other queries in SDQL.

[amascolo]

@amirsh this PR is now ready to merge, subject to your approval:

• Supports all sort-based and hybrid JOB queries in SDQL ✅
• Performance within 2% of C++ (no regression on hash-based queries)