Fix potential JarFileEntries ClassCastException

Update `JarFileEntries` so that the interface is obtained rather than
the concrete implementation. This allows `JarEntry` values to be used
without causing a ClassCastException.

Closes gh-19041

Author: philwebb

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarFileEntries.java

@@ -370,7 +370,7 @@ private int getEntryIndex(CharSequence name) {
 		int hashCode = AsciiBytes.hashCode(name);
 		int index = getFirstIndex(hashCode);
 		while (index >= 0 && index < this.size && this.hashCodes[index] == hashCode) {
-			CentralDirectoryFileHeader candidate = getEntry(index, CentralDirectoryFileHeader.class, false, null);
+			FileHeader candidate = getEntry(index, FileHeader.class, false, null);
 			if (candidate.hasName(name, NO_SUFFIX)) {
 				return index;
 			}