Add separate constants `TEXTALIGN_TOP`, `TEXTALIGN_MIDDLE` and `TEXTALIGN_BOTTOM` for vertical alignment.
Add shorthand constants for all possible combinations of horizontal and vertical alignment, e.g. `TEXTALIGN_MC` for `TEXTALIGN_MIDDLE | TEXTALIGN_CENTER`.
Replace usage of `SLabelProperties::m_AlignVertically` with these constants in all menu and editor code for more convenient and versatile alignment of text. Use combined horizontal-vertical alignment constants for all existing labels. Manually adjust layout for some elements which were initially misaligned with the new implementation.
Refactoring:
- Use `CORNER_NONE` instead of `0`.
- Improve some `CUIRect` variables names and usage.