Code profiling and bechmarking

[smishr]

Optimise computation or allocation intensive functions and algorithms in the main codebase.

Review important computation intensive functions like

• [ ] bootweights
• [ ] bydomain
• [ ] ReplicateDesign
• [ ] SurveyDesign

Pre-allocation like here also helps optimise runtime, especially in memory heavy operations on DataFrames like adding new replicate weights