PR summary

closes #32005

Axis.get_tick_space() estimates the number of ticks that fit on an axis
by dividing the available length by an estimated tick label size. That
estimate assumes tick labels are drawn horizontally (a fixed aspect-ratio
heuristic: 3:1 for the x-axis, 2:1 for the y-axis), so rotating labels via
tick_params(rotation=...) produces poor tick spacing, as shown in the
linked issue's reproduction.

This PR makes the estimate aware of label rotation:

• Added Axis._get_tick_label_rotation(), which reads the rotation angle
  stored in _major_tick_kw['labelrotation'] (set via tick_params).

• XAxis.get_tick_space() and YAxis.get_tick_space() now blend the
  aspect-ratio heuristic between the horizontal and vertical cases using
  the rotation angle:

  aspect = |horizontal_factor * cos(theta)| + |vertical_factor * sin(theta)|

  At theta = 0 this is identical to the current behavior, so unrotated
  labels are unaffected. As rotation approaches 90 degrees, the x-axis
  estimate shrinks towards a single line-height, and the y-axis estimate
  grows towards the horizontal-text ratio.

This keeps the estimate cheap (no actual text measurement is performed),
consistent with the existing design intent noted in
_get_tick_label_size's docstring, which avoids creating a Tick object
for performance reasons.

AI Disclosure

I used an AI assistant (Claude) as a tutor while working on this: to help
me understand how get_tick_space and the tick-rotation storage in
_major_tick_kw work, to talk through possible approaches (including a
simpler threshold-based alternative I considered and decided against),
and to help troubleshoot my local dev environment setup. I wrote and
reviewed the final diff myself and understand the reasoning behind it.

PR checklist

• "closes [Bug]: Axis.get_tick_space could take tick label rotation into account #32005" is in the body of the PR description
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines