Add a new check API that does not wrap the domain check EPP flow

Copied class and test from CheckApiAction. All unit tests passing.

Remaining work: add metrics

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=198916177

java/google/registry/config/RegistryConfig.java

@@ -1101,9 +1101,8 @@ public final class RegistryConfig {
       return config.registryPolicy.reservedTermsExportDisclaimer;
     }
 
-    /**
-     * Returns the clientId of the registrar used by the {@code CheckApiServlet}.
-     */
+    /** Returns the clientId of the registrar used by the {@code CheckApiServlet}. */
+    // TODO(b/80417678): remove this once CheckApiAction no longer uses this id.
     @Provides
     @Config("checkApiServletRegistrarClientId")
     public static String provideCheckApiServletRegistrarClientId(RegistryConfigSettings config) {