layout: Fix depends_on_block_constraints logic (#38318)

The logic was wrong, sometimes we weren't setting it to true on flex
containers that needed it, and then as a workaround we were setting it
to to true on flex items that didn't need it.

For example, this testcase had 5 cache misses when stretching the items,
now we will avoid laying them out again:
```html
<div style="display: flex">
  <div></div>  <div></div>  <div></div>  <div></div>  <div></div>
</div>
```

Also, the workaround wasn't always working, e.g. it failed to stretch
the green element here:
```html
<div style="display: flex; min-height: 200px">
  <div>
    <div style="display: flex; height: 100%; background-color: red">
      <div style="width: 200px; background-color: green;"></div>
    </div>
  </div>
</div>
```

Testing: Adding new test
Fixes: #38023

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

tests/wpt/meta/MANIFEST.json

@@ -183398,6 +183398,19 @@
        {}
       ]
      ],
+     "stretched-child-in-nested-flexbox-003.html": [
+      "7f8cd10da3afd7812353ac39eff15194f328058a",
+      [
+       null,
+       [
+        [
+         "/css/reference/ref-filled-green-200px-square.html",
+         "=="
+        ]
+       ],
+       {}
+      ]
+     ],
      "stretching-orthogonal-flows.html": [
       "acaa787faf657b76a5b213fb9203088d5d28f4c4",
       [