Treat URLs for same file in nested archive and from jar root as equal

Consider the following two URLs:

jar:file:/test.jar!/BOOT-INF/classes!/foo.txt
jar:file:/test.jar!/BOOT-INF/classes/foo.txt

They both reference the same foo.txt file in the BOOT-INF/classes
directory of test.jar, however the first URL does so via the
nested BOOT-INF/classes archive. Previously, this difference in the
URLs would lead to PathMatchingResourcePatternResolver returning two
resources for foo.txt when asked to find all resources matching the
pattern classpath*:/**/*.txt.

This commit updates our Handler that is used for jar: URLs to consider
the two URLs above to be equivalent such that url1 is equal to url2
and the two urls will produce the same hash code.

Closes gh-7449

spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/HandlerTests.java

@@ -119,6 +119,23 @@ public class HandlerTests {
 				new URL("jar:file:/the/path/to/the/first.jar!/content.txt"))).isTrue();
 	}
 
+	@Test
+	public void sameFileReturnsTrueForUrlsThatReferenceSameFileViaNestedArchiveAndFromRootOfJar()
+			throws MalformedURLException {
+		assertThat(this.handler.sameFile(
+				new URL("jar:file:/test.jar!/BOOT-INF/classes!/foo.txt"),
+				new URL("jar:file:/test.jar!/BOOT-INF/classes/foo.txt"))).isTrue();
+	}
+
+	@Test
+	public void hashcodesAreEqualForUrlsThatReferenceSameFileViaNestedArchiveAndFromRootOfJar()
+			throws MalformedURLException {
+		assertThat(this.handler
+				.hashCode(new URL("jar:file:/test.jar!/BOOT-INF/classes!/foo.txt")))
+						.isEqualTo(this.handler.hashCode(
+								new URL("jar:file:/test.jar!/BOOT-INF/classes/foo.txt")));
+	}
+
 	private URL createUrl(String file) throws MalformedURLException {
 		return new URL("jar", null, -1, file, this.handler);
 	}