Add remove buttons for mod entries in custom preset lists

[CloneWith]

Changes

To make it easier for users to remove unwanted mods in a custom mod preset.

• Add remove buttons to the left of a mod entry, with a static tooltip
• Block removing action and make the entry flash red when there is only one mode left in a preset

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By the way should we consider add a Use current mods in the context menu? Thus we don't need to open the editor popup to apply mods to a preset.

Known Problems

• Since we pass a fixed hashset to the mod row, it's unable to change the state of the remove button. I'm considering using a Bindable<Hashset<Mod>> for that.
• The use of LocalisableString for tooltip text is being considered.