Conflict highlight for selected row

[HebaruSan]

Problems / Motivations

• If you select to install two mods that conflict, their background color properties are set to a reddish color, but this is completely overridden by the blue row highlight color. If the other conflicting mod's row is off-screen, this usually meant that you couldn't see any red highlights at all.
• Conflict descriptions are missing from the status bar in some cases
• If you apply multiple labels to a mod, only one of their background colors is applied

Causes

• RelationshipResolver.ConflictDescriptions only returned descriptions of conflicts for the mod with fewer indirectly-depending mods, intended to choose the conflict closest to what the user selected, but when these values were equal, neither would appear.

Changes

• Now if two conflicting mods have equal numbers of indirectly-depending mods, both of their description conflicts are shown in the status bar
• Now if you select a row with a conflict, the red color is blended 75%/25% with the highlight color, producing a reddish purple color that can still be recognized as conflict-y:
  
  The red conflict color has had its green and blue channels roughly halved to make this work a bit better.
• Similar to the above, a background color from a label is also blended 75%/25% with the highlight color so you can still tell a label has been applied while the row is highlighted
• Now if you apply multiple labels, their colors are blended together, and the labels menu shows the colors of the labels:
  

Fixes #3947.

[HebaruSan]

Self-reviewing so we can include this in the hotfix release...