layout: Remove min and max container sizes from FlexContext (#35144)

Thanks to #34946 we don't have to recompute the min and max sizes, we
can get them from the `ContainingBlock`.

And then in `FlexContext` there is no need to store both the definite
and the min & max sizes of the container`, we can instead make do with
a single `FlexRelativeVec2<SizeConstraint>`.

This removes 1 of the 3 usages of `ContentBoxSizesAndPBMDeprecated`,
which is also good.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/flexbox/geom.rs

@@ -14,6 +14,15 @@ pub(super) struct FlexRelativeVec2<T> {
     pub cross: T,
 }
 
+impl<T> FlexRelativeVec2<T> {
+    pub fn map<U>(&self, f: impl Fn(&T) -> U) -> FlexRelativeVec2<U> {
+        FlexRelativeVec2 {
+            main: f(&self.main),
+            cross: f(&self.cross),
+        }
+    }
+}
+
 #[derive(Clone, Copy, Debug)]
 pub(super) struct FlexRelativeSides<T> {
     pub cross_start: T,