UI: Gray out fade inactive geometry overlay slider when off

The slider should be inactive when the setting is turned off like
the wireframe slider.

Cleanup: Fix clang tidy inconsistent parameter warning

UI: Always set curve fill mode inactive for object bevel type

The bevel type is a more useful check for graying out this property
because its effects will be apparent before choosing an object. Before,
the fill type property would only gray out with a bevel object selected.

Cleanup: Use shorthand variables

We don't use the other variables in the sorting struct,
so we might as well use the panels directly.

Property Search: Don't set expansion for panels in inactive tabs

The search should check if a panel is active before changing its
expansion, otherwise it sets the expansion for all of the region's
panels, even invisible ones in other tabs.

UI: Remove colons in property names

UI: Use property split in UV editor panels

This is not an exhaustive change, just for the 2D cursor and
UDIM grid properties. Also vertically align the "UV Vertex"
buttons like in the 3D view panels.

Curves: Allow caps for all geometry types

I think this wasn't allowed before because the section of a curve was
built in multiple parts. But since rBe34d3e32dda7, the whole slice
of a curve is built in one piece, so we can easily support curve
caps for all geometry types, including the new custom profile option.

Note that this also allows "caps" when the fill type is not full.
They could easily be disabled by checking for "Full" fill type
if that was preferred in the future.

See the patch for images.

Differential Revision: https://developer.blender.org/D8911

Fix 80909: Switching to profile bevel can explode Curve geometry

We need to make sure the CurveProfile is initialized with the proper
number of segments when switching to profile bevel mode.

UI: Refactor panel alignment function

This code had grown overly complicated and hard to understand.
The improvements in this commit:
- Avoid allocating a duplicate of every active panel.
- Instead of complicated logic to calculate each panel's offset,
just keep track of the current offset while iterating through.
- More readable code structure, better comments.

Note that calcuting the X offset here is a relic from pre-2.5 when
panels could be aligned horizontally. I kept this in, but it would
be reasonable to remove it in the future.