Reset grid for eqdsk.

[geograham]

Description of issue / requirement to address

If a large, fine grid is used then the Equilibrium object will be too large for typical laptop memory.

Proposed solution

The option of resetting the grid size in the eqdsk file before using it to create an Equilibrium object.

Additional context

• Associated issue: Does psi and jtor need to be reinited in Equlibrium #3576

• We may still want to have a reset_grid function in Equilibrium and FixedPlasmaEquilibrium.

[je-cook]

An attempt to do this is #3890