Oatmeal, Fig, and Walnut Bars

Filling:

• 2 cups chopped stemmed dried figs (10 to 11 ounces)
• 1 cup water
• 6 tablespoons sugar
• Pinch of salt
• 1 1/2 teaspoons fresh lemon juice
• 1 teaspoon vanilla extract
• 1 cup walnuts, toasted, coarsely chopped

Crust:

• Nonstick vegetable oil spray
• 1 3/4 cups old-fashioned oats
• 13/4 cups all purpose flour
• 1 1/4 cups (packed) dark brown sugar
• 2 teaspoons ground cinnamon
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 cup (2 sticks) chilled vegan "butter" (such as Earth Balance) or margarine, cut into 1/2-inch cubes
• 1 cup powdered sugar