Migrate endpoints.cors to management.endpoints.cors

This commit moves CORS properties out of the endpoints namespace as they
do not refer to a "cors" endpoint but rather to the CORS configuration
of all endpoints.

Closes gh-10053

spring-boot-samples/spring-boot-sample-actuator/src/test/resources/application-cors.properties

@@ -1,2 +1,2 @@
-endpoints.cors.allowed-origins=http://localhost:8080
-endpoints.cors.allowed-methods=GET
+management.endpoints.cors.allowed-origins=http://localhost:8080
+management.endpoints.cors.allowed-methods=GET