feat: add support for StyleSheet annotation hotswap (#22741)

Implements hotswap for changes related to the StyleSheet annotation.
Reacts on adding, removing or updating the value of the annotation
on AppShellConfigurator and Component subclasses, by registering
or unregistering the stylesheet with the API provided by UI and
UIInternals classes

Fixes #22631

Author: mcollovati

flow-client/src/main/java/com/vaadin/client/ResourceLoader.java

@@ -281,6 +281,11 @@ private void initLoadedResourcesFromDom() {
                     || "import".equalsIgnoreCase(rel)) && href != null
                     && href.length() != 0) {
                 loadedResources.add(href);
+                // Handle stylesheet loaded by AppShellRegistry
+                String dependencyId = linkElement.getAttribute("data-id");
+                if (dependencyId != null) {
+                    dependencyIdToResourceKey.set(dependencyId, href);
+                }
             }
         }
     }