PR summary

Closes #25789, see there for detailed discussion of what changed

This is addressing the extremely small (literally Unit of Least Precision, ULP) changes to how numpy computes sin/cos on main.
Through a combination of ratios of small numbers and relying on precise edge case behavior in tests of floats, we saw 3 cases where the miniscule difference compounded to test failures.

Two cases of projections having degenerate points where the edge case is inherently unstable:

• Mollweide projection is degenerate at the poles, we were lucky that the floating point operations precisely canceled
  • Fixed by just not testing round tripping of the poles, as they shouldn't necessarily round trip
• Formatting of polar coordinates
  • Polar coordinates are degenerate at r=0, thus we were relying on boundary behavior to get zero decimals of precision
  • Does an absolute difference mod 2 pi, thus the maximum possible is pi, and then divides by pi, thus the only way to get the tested precision was to get exactly np.pi
    • The only place this can actually happen in adjacent pixels is around the origin
  • The method is used for tool tip in interactive plotting, and precisely placing the mouse at 0,0 is unlikely to impossible depending on resolution, etc
  • Fixed by moving the radius out far enough that we are no longer degenerate and have stable expected precision

one case of attempting to do equality checks on processed floats:

• Round tripping of 3d axis colors with light source at 90 degrees
• since pi/2 is imprecise (because all floats except sums of powers of two are) there should be some allowance for float precision error
• The tolerance is still really tight (4 ULPs, or a relative tolerance of ~1e-15)

PR checklist

• "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New Features and API Changes are noted with a directive and release note
• [N/A] Documentation complies with general and docstring guidelines