ComboBox is now wrapped in horizontal_wrap container

[WojciechMula]

Describe the bug

When a combo boxes are placed in wrapping container, they do not wrap when the container size shrinks.

To Reproduce
I modified Layout Test from demo app in the following way (just added few buttons and combo boxes):

diff --git a/crates/egui_demo_lib/src/demo/layout_test.rs b/crates/egui_demo_lib/src/demo/layout_test.rs
index a5726c7a..ee04f0a1 100644
--- a/crates/egui_demo_lib/src/demo/layout_test.rs
+++ b/crates/egui_demo_lib/src/demo/layout_test.rs
@@ -180,5 +180,42 @@ fn demo_ui(ui: &mut Ui) {
     let mut dummy = false;
     ui.checkbox(&mut dummy, "checkbox");
     ui.radio_value(&mut dummy, false, "radio");
-    let _ = ui.button("button");
+    let _ = ui.button("button1");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button3");
+
+    let alternatives = ["a", "b", "c", "d"];
+    let mut selected = 2;
+    egui::ComboBox::from_label("combobox1").show_index(
+        ui,
+        &mut selected,
+        alternatives.len(),
+        |i| alternatives[i]
+    );
+
+    let mut selected = 2;
+    egui::ComboBox::from_label("combobox2").show_index(
+        ui,
+        &mut selected,
+        alternatives.len(),
+        |i| alternatives[i]
+    );
+
+    let mut selected = 2;
+    egui::ComboBox::from_label("combobox3").show_index(
+        ui,
+        &mut selected,
+        alternatives.len(),
+        |i| alternatives[i]
+    );
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button2");
+    let _ = ui.button("button3");
 }

Expected behavior
Checkboxes should behave like other widgets.

Screenshots
I recorded the modified demo app: https://youtu.be/O5CnZ1KF8D4