Make tracing solver controls configurable

[rogeriojorge]

What changed

• Add max_steps and progress_meter controls to Tracing.
• Replace the effectively unbounded 10_000_000_000 Diffrax limit with a configurable default of 1_000_000 steps.
• Apply that limit consistently to all eight Diffrax solve branches, including guiding-center, collision, field-line, and full-orbit integrations.
• Use NoProgressMeter by default while allowing callers to pass a Diffrax progress meter explicitly.
• Honor caller-provided rejected_steps and event condition values.

Scope

This PR contains only generic solver-control and constructor-default changes. It is independent of the VMEC magnetic-axis fix in #47 and does not change any model equations, coordinate handling, or loss classification.

FullOrbit_Boris is not a Diffrax solve and therefore does not use max_steps; its iteration count remains determined by the requested output-time array.

Validation

• python -m pytest tests/test_dynamics.py -q: 14 passed
• wout_nfp3_final_scaled.nc, GuidingCenter, 10 particles, tmax=1e-4: completed in 1.68 s with trajectory shape (10, 21, 4) and 0% loss
• Verified every diffeqsolve call receives self.max_steps