Move data structure to dataclasses

[clmould]

Thanks to @timothy-nunn's work in #4120, we can convert the remaining global data structures to dataclasses.

This will be split into several pull requests

• Move water use data structure to a dataclass #4120
• Implement Model ABC on all models #4146
• move costs 2015 data structure to dataclass #4153
• cs fatigue data class and setting up use of datastructure elsewhere t… #4173

Below are the data structure conversions that need doing. Will add to the PR list above when working on them

• Implement Model ABC on all models
• blanket_library.py
• build_variables.py
• buildings_variables.py
• ccfe_hcpb_module.py
• constraint_variables.py
• cost_2015_variables.py
• cost_variables.py
• cs_fatigue_variables.py
• current_drive_variables.py
• dcll_variables.py
• divertor_variables.py
• first_wall_variables.py
• fwbs_variables.py
• global_variables.py
• heat_transport_variables.py
• ife_variables.py
• impurity_radiation_module.py
• neoclassics_variables.py
• numerics.py
• pf_power_variables.py
• pfcoil_variables.py
• physics_variables.py
• power_variables.py
• primary_pumping_variables.py
• pulse_variables.py
• rebco_variables.py
• reinke_variables.py
• scan_variables.py
• stellarator_configuration.py
• stellarator_variables.py
• structure_variables.py
• superconducting_tf_coil_variables.py
• tfcoil_variables.py
• times_variables.py
• vacuum_variables.py
• water_usage_variables.py