[3.x] Tweak editor icons for navigation nodes and SkeletonIK

[timothyqiu]

Backport of #62201

Updated snapshot in #62246 (comment)

[YuriSizov]

A nitpick, but I think the colors are off and need to be less saturated for this version of Godot. You can clearly see the pink and the blue are different from their base node counterparts.

[Calinou]

A nitpick, but I think the colors are off and need to be less saturated for this version of Godot. You can clearly see the pink and the blue are different from their base node counterparts.

Indeed, a 1:1 color match is also required for dark → light theme conversion to work.

[timothyqiu]

TIL the tint colors are different between 4.0 and 3.x :) Adjusted the colors to be the same as their base icons:

Dark	Light

[Calinou]

TIL the tint colors are different between 4.0 and 3.x :) Adjusted the colors to be the same as their base icons:

For reference, this change was initially made in #48644. It wasn't remade for 3.x as we want the editor theme to be distinguishable between 3.x and 4.0 (so tutorials' version can be recognized instantly).

[akien-mga]

Thanks!