Allow template lookup caching to be disabled

Extract TemplateAvailabilityProvider caching logic to a new
TemplateAvailabilityProviders class and provide property support to
disable it. Also update DevToolsPropertyDefaultsPostProcessor to
automatically set the property.

Fixes gh-5989

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java

@@ -51,6 +51,7 @@ public class DevToolsPropertyDefaultsPostProcessor implements EnvironmentPostPro
 		properties.put("server.session.persistent", "true");
 		properties.put("spring.h2.console.enabled", "true");
 		properties.put("spring.resources.cache-period", "0");
+		properties.put("spring.template.provider.cache", "false");
 		PROPERTIES = Collections.unmodifiableMap(properties);
 	}