Restore TomcatHeadersAdapter.clear() behavior

This commit restores the original behavior of the clear() method in
TomcatHeadersAdapter by delegating to
org.apache.tomcat.util.http.MimeHeaders.recycle(), which aligns with
the memory efficiency goals documented in the class-level Javadoc for
MimeHeaders.

See gh-33916
Closes gh-34092

spring-web/src/main/java/org/springframework/http/server/reactive/TomcatHeadersAdapter.java

@@ -163,9 +163,7 @@ public void putAll(Map<? extends String, ? extends List<String>> map) {
 
 	@Override
 	public void clear() {
-		while (this.headers.size() > 0) {
-			this.headers.removeHeader(0);
-		}
+		this.headers.recycle();
 	}
 
 	@Override

spring-web/src/test/java/org/springframework/http/server/reactive/TomcatHeadersAdapterTests.java

@@ -25,17 +25,25 @@
  * Tests for {@link TomcatHeadersAdapter}.
  *
  * @author Johnny Lim
+ * @author Sam Brannen
+ * @since 7.0
  */
 class TomcatHeadersAdapterTests {
 
+	private final TomcatHeadersAdapter adapter = new TomcatHeadersAdapter(new MimeHeaders());
+
+
 	@Test
 	void clear() {
-		MimeHeaders mimeHeaders = new MimeHeaders();
-		TomcatHeadersAdapter adapter = new TomcatHeadersAdapter(mimeHeaders);
 		adapter.add("key1", "value1");
 		adapter.add("key2", "value2");
+		assertThat(adapter).isNotEmpty();
+		assertThat(adapter).hasSize(2);
+		assertThat(adapter).containsKeys("key1", "key2");
+
 		adapter.clear();
 		assertThat(adapter).isEmpty();
+		assertThat(adapter).hasSize(0);
 	}
 
 }