IS Remaining TODOs for Second Cost Refactor

[GabrielKS]

This is a list of TODOs that remain unfinished from #344, they should all be addressed before IS is released.

• The function get_raw_data is not type stable (see #359
• In retransform_hdf_array, use of map rather than preallocation might be a performance issue (see

  InfrastructureSystems.jl/src/hdf5_time_series_storage.jl

  Line 708 in aabe967

  return map(x -> T(x...), eachslice(data; dims = dims_to_keep)) # PERF possibly preallocation would be better

  etc.).
• Possible further type stability issues in transform_array_for_hdf, see review comment https://github.com/NREL-Sienna/InfrastructureSystems.jl/pull/344/files/241514d1b15282f1259f9a780b2c62a8fb4c6238#r1567689474
• Fix convert_data as per Second Cost Refactor: Companion PR (+add serialization for @scoped_enum, add NotImplementedError) #344 (comment)

These seem to all be potential performance issues.