Extend ArchitectureCheck with NullMarkedExtension

Introduce NullMarkedExtension for ArchitectureCheck, which provides
functionality to configure packages to ignore in nullability checks and
to enable or disable the extension.

See gh-47596

Signed-off-by: Dmytro Nosan <dimanosan@gmail.com>

cli/spring-boot-cli/build.gradle

@@ -62,7 +62,10 @@ dependencies {
 }
 
 architectureCheck {
-	nullMarked = false
+	nullMarked {
+		enabled  = false
+		ignoredPackages = ['org.springframework.boot.cli.json']
+	}
 }
 
 tasks.register("fullJar", Jar) {