Use StringUtils.uriDecode where feasible

[nosan]

See #44945

[nosan]

Unfortunately, because of the following error, org.springframework.boot.loader.net.util.UrlDecoder cannot be replaced

Using start class org.test.SampleApplicationUsing destination directory /Users/dmytronosan/IdeaProjects/spring-boot/build-plugin/spring-boot-antlib/build/it/sample/targetExtracting spring-boot-loader to /Users/dmytronosan/IdeaProjects/spring-boot/build-plugin/spring-boot-antlib/build/it/sample/target/dependencyCopying 1 resource to /Users/dmytronosan/IdeaProjects/spring-boot/build-plugin/spring-boot-antlib/build/it/sample/target/dependencyEmbedding spring-boot-loader v4.0.0-SNAPSHOT...Building jar: /Users/dmytronosan/IdeaProjects/spring-boot/build-plugin/spring-boot-antlib/build/it/sample/target/found.jarChecking 
/Users/dmytronosan/IdeaProjects/spring-boot/build-plugin/spring-boot-antlib/build/it/sample/target/found.jarException 
in thread "main" java.lang.NoClassDefFoundError: org/springframework/util/StringUtils
at org.springframework.boot.loader.net.protocol.nested.NestedLocation.fromUrl(NestedLocation.java:79)
at org.springframework.boot.loader.net.protocol.nested.NestedUrlConnection.parseNestedLocation(NestedUrlConnection.java:79)
at org.springframework.boot.loader.net.protocol.nested.NestedUrlConnection.<init>(NestedUrlConnection.java:72)
at org.springframework.boot.loader.net.protocol.nested.NestedUrlConnection.<init>(NestedUrlConnection.java:67)
at org.springframework.boot.loader.net.protocol.nested.Handler.openConnection(Handler.java:48)
at java.base/java.net.URL.openConnection(URL.java:1206)
at org.springframework.boot.loader.net.protocol.jar.JarUrlConnection.<init>(JarUrlConnection.java:88)
at org.springframework.boot.loader.net.protocol.jar.JarUrlConnection.open(JarUrlConnection.java:353)
at org.springframework.boot.loader.net.protocol.jar.Handler.openConnection(Handler.java:46)
at java.base/java.net.URL.openConnection(URL.java:1206)
at org.springframework.boot.loader.net.protocol.jar.JarUrlClassLoader.getJarFile(JarUrlClassLoader.java:183)
at org.springframework.boot.loader.net.protocol.jar.JarUrlClassLoader.definePackage(JarUrlClassLoader.java:146)
at org.springframework.boot.loader.net.protocol.jar.JarUrlClassLoader.definePackageIfNecessary(JarUrlClassLoader.java:129)
at org.springframework.boot.loader.net.protocol.jar.JarUrlClassLoader.loadClass(JarUrlClassLoader.java:102)
at org.springframework.boot.loader.launch.LaunchedClassLoader.loadClass(LaunchedClassLoader.java:91)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:543)
at org.springframework.boot.loader.launch.Launcher.launch(Launcher.java:99)
at org.springframework.boot.loader.launch.Launcher.launch(Launcher.java:64)
at org.springframework.boot.loader.launch.JarLauncher.main(JarLauncher.java:40)Caused by: java.lang.ClassNotFoundException: org.springframework.util.StringUtils
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:580)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)	... 21 moreJava Result: 1

[nosan]

My initial proposal was nosan@2f91fe2, but these changes break the spring-boot-antlib build due to the error that I commented on above.

[snicoll]

@nosan given we can't access spring-core in the loader and we want to avoid inconsistencies, I rather copied over Spring Framework's equivalent. This would expand its use and potentially help us refine the current algorithm.