layout: Allow lazy resolution of automatic minimum sizes (#35965)

`Size::resolve_for_min()` had an `Au` parameter, representing the value
to be used for an automatic minimum size. However, this amount isn't
trivial to compute in flexbox, so this patch changes the parameter to a
function that can be called lazily.

Note flexbox isn't currently using `Size::resolve_for_min()`, but it
will in #35961.

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

components/layout_2020/replaced.rs

@@ -538,7 +538,7 @@ impl ReplacedContents {
         let inline_size = sizes.inline.resolve(
             Direction::Inline,
             automatic_size.inline,
-            Au::zero(),
+            Au::zero,
             Some(inline_stretch_size),
             get_inline_content_size,
             false, /* is_table */
@@ -558,7 +558,7 @@ impl ReplacedContents {
         let block_size = sizes.block.resolve(
             Direction::Block,
             automatic_size.block,
-            Au::zero(),
+            Au::zero,
             block_stretch_size,
             || *block_content_size,
             false, /* is_table */