Quench detection time calculation

We should be able to calculate the detection time of a quench even from a physics basis, rather than treat it as a user input.

Phase 1 (detection time): current held constant until the electric field across the conductor reaches a specified threshold.

• The duration of this phase, t₁, can be calculated numerically.
• This requires integrating temperature-dependent resistivity and heat capacity until the threshold is reached.
• The result gives both the detection time and the temperature of the normal zone at the end of Phase 1.

See #523 https://github.com/ukaea/PROCESS/issues/523 for full context

Reference Material:

• 2-phase_quench_model.pdf
• https://arxiv.org/abs/1401.3927