Revert "Ignore unknown plugin options in REST endpoints that support dynamic options"

This reverts commit 6210be243d.

We are currently discussing alternative solutions [1] and want to start
from scratch once we decided which one we like most.

[1] https://gerrit-review.googlesource.com/c/gerrit/+/231004/2//COMMIT_MSG

Change-Id: I906eac5eef2e7163a608227d4822984474bdf413

java/com/google/gerrit/util/cli/UnknownOptionHandler.java

@@ -25,22 +25,6 @@ import com.google.gerrit.common.Nullable;
  * behavior if classes do not implement this interface).
  */
 public interface UnknownOptionHandler {
-  /**
-   * Checks whether the given option name matches the naming pattern of options that are defined by
-   * plugins that were defined by registering a {@link
-   * com.google.gerrit.server.DynamicOptions.DynamicBean}.
-   *
-   * @param optionName name of the option
-   * @return {@code true} if it's a plugin option, otherwise {@code false}
-   */
-  public static boolean isPluginOption(String optionName) {
-    // Options from plugins have the following name pattern: '--<plugin-name>--<option-name>'
-    if (optionName.startsWith("--")) {
-      optionName = optionName.substring(2);
-    }
-    return optionName.contains("--");
-  }
-
   /**
    * Whether an unknown option should be accepted.
    *