Remove reflective validation from ReplaceStringLiteralWithConstant

The validate() method used Class.forName() to reflectively verify that
the target constant exists when literalValue was not provided. This
fails when the target class is not on the recipe classpath, which is
the common case (e.g. org.springframework.http.MediaType is not a
dependency of rewrite-spring), producing errors like:

  fullyQualifiedConstantName was
  'org.springframework.http.MediaType.TEXT_HTML_VALUE' but it
  No class for specified name was found.

The reflective fallback in getLiteralValue() already handles this
gracefully by returning null, causing getVisitor() to return a noop.
Validation should not reject the recipe for a condition that the
runtime already handles.

Author: timtebeek

rewrite-java/src/main/java/org/openrewrite/java/ReplaceStringLiteralWithConstant.java

@@ -69,25 +69,6 @@ public Validated<Object> validate() {
         if (StringUtils.isBlank(fullyQualifiedConstantName)) {
             return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "The constant's fully qualified name may not be empty or blank."));
         }
-        if (StringUtils.isBlank(literalValue)) {
-            try {
-                Object constantValue = getConstantValueByFullyQualifiedName(fullyQualifiedConstantName);
-                if (constantValue == null) {
-                    return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "Provided constant should not be null."));
-                }
-                if (!(constantValue instanceof String)) {
-                    // currently, we only support string literals, also see visitor implementation
-                    return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "Unsupported type of constant provided. Only literals can be replaced."));
-                }
-                return result;
-            } catch (ClassNotFoundException e) {
-                return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "No class for specified name was found."));
-            } catch (NoSuchFieldException e) {
-                return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "No field with specified name was found."));
-            } catch (IllegalAccessException e) {
-                return result.and(invalid(CONSTANT_FQN_PARAM, fullyQualifiedConstantName, "Unable to access specified field."));
-            }
-        }
         return result;
     }