Switch to ImageListView and minor UI/UX improvements

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• Now using ImageListView NuGet package in place of the ListView class for textures. This doesn't have jittery scrolling, looks cleaner, doesn't scale the textures poorly, and acts faster overall. The only trade-offs is that some of the control's functionality is awkward to use/jank.
• Changed Textures, VRAM, and Animations splitters to be fixed to panel2, meaning the lower part won't resize when resizing the window.
• VRAM's splitter can no longer be changed, and now has a position that puts the buttons at the bottom of the panel.
• DialogForm now finishes when enter is pressed, and cancels when X is pressed. Null is returned when cancelled.
• DialogForm now has a defaultText option (which will select the whole text).
• Created AskForVRAMPage function to replace both cases where a VRAM page is asked for.