Try TMT_IMAGEFILE first when drawing part background and the part contains glyph images.
Otherwise, search TMT_IMAGEFILE1~7 and then TMT_IMAGEFILE or TMT_GLYPHIMAGEFILE. This behavior can
be verified by drawing scroll bar arrow buttons, where TMT_IMAGEFILE is used for background despite
TMT_IMAGEFILE1 being present and TMT_IMAGEFILE1 is used for glyphs despite TMT_IMAGEFILE is present.
For parts without glyph images, TMT_IMAGEFILE1~7 are always searched first, then try TMT_IMAGEFILE
or TMT_GLYPHIMAGEFILE.

Fix the size grip on status control not being painted when using builtin Light theme. The status
gripper part uses TMT_IMAGEFILE1~7 and doesn't have TMT_IMAGEFILE. So when UXTHEME_SelectImage()
tries to query TMT_IMAGEFILE for status gripper, it falls back to using status class TMT_IMAGEFILE.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>