Deprecate PathResource variant

This commit deprecates the `PathResource` implementation variant in
favor of `FileSystemResource`. This was already pointing to
`FileSystemResource` as of Spring Framework 5.1 and we now consider this
variant as deprecated.

Closes gh-34206

spring-core/src/test/java/org/springframework/core/io/PathResourceTests.java

@@ -50,6 +50,7 @@ import static org.mockito.Mockito.mock;
  * @author Juergen Hoeller
  * @author Arjen Poutsma
  */
+@SuppressWarnings("removal")
 class PathResourceTests {
 
 	private static final String TEST_DIR =