Generic Agg will take a candle factory rather than rely on Default

[dam5h]

This adds more flexibility in the types we can aggregate in case we need runtime parameters as part of that logic.

Changes:

• 🦚 Feature

References:

Changes proposed by this PR:

Removed the trait bound for Default on the generic aggregators candle type, instead the new(...) method will take a zero argument closure.

📜 Checklist

• [x] The PR scope is bounded
• [x] Relevant issues and discussions are referenced
• [x] Test coverage is excellent and passes
• [x] Tests test the desired behavior
• [x] Documentation is thorough