The logic for this was duplicated, in two very different forms,
between the SCH_PIN bounding box function and the
SCH_PAINTER draw function.
And the SCH_PIN one was slightly wrong, as it didn't take into
account the PIN_TEXT_MARGIN, or the electrical types.
Provide a way for clients of the PIN_LAYOUT_CACHE to access
the name and number boxes.
The bounding box calculations of SCH_PINs are pretty complicated.
There is already caching of the name and number texts, but the
SCH_PAINTER (for example) has to repeat this work and sometimes
slightly diverges. For example, dangling indicators and alt
icons are painted, but not included in the bbox.
This commit introduces a more encapsulated 'layout cache' object which will
take care of caching the current extents, but also providing layout
geometry to SCH_PAINTER (and other interested code, like hit testers
on a given field) witohut requiring recomputation or reimplementation.
The extents calculations use exclusively the public API, so it's nice
and easy to split it out.
In this commit, nothing is functionally changed - the name and number
are still cached, and everything else is computed in the exact same way.
This is the groundwork for fixing this issue:
Relates-To: https://gitlab.com/kicad/code/kicad/-/issues/18894
