Remove internal map-only enum

We took a change that added an enum that was used purely for mapping from
EventInfo.type to GHEvent. This seemed fine but that enum is used only by EventInfo.

This change removed that enum and adds a map to EventInfo to do the required mapping.
This avoids shoehorning mapping behavior in to the EnumUtils.

src/main/java/org/kohsuke/github/GHEvent.java

@@ -1,11 +1,7 @@
 package org.kohsuke.github;
 
-import org.kohsuke.github.internal.EnumUtils;
-
 import java.util.Locale;
 
-import javax.annotation.Nonnull;
-
 /**
  * Hook event type.
  *
@@ -91,46 +87,4 @@ public enum GHEvent {
             return "*";
         return name().toLowerCase(Locale.ENGLISH);
     }
-
-    /**
-     * Representation of GitHub Event Type
-     *
-     * @see <a href="https://docs.github.com/en/developers/webhooks-and-events/github-event-types">GitHub event
-     *      types</a>
-     */
-    enum GitHubEventType {
-        CommitCommentEvent(COMMIT_COMMENT),
-        CreateEvent(CREATE),
-        DeleteEvent(DELETE),
-        ForkEvent(FORK),
-        GollumEvent(GOLLUM),
-        IssueCommentEvent(ISSUE_COMMENT),
-        IssuesEvent(ISSUES),
-        MemberEvent(MEMBER),
-        PublicEvent(PUBLIC),
-        PullRequestEvent(PULL_REQUEST),
-        PullRequestReviewEvent(PULL_REQUEST_REVIEW),
-        PullRequestReviewCommentEvent(PULL_REQUEST_REVIEW_COMMENT),
-        PushEvent(PUSH),
-        ReleaseEvent(RELEASE),
-        WatchEvent(WATCH),
-        UnknownEvent(UNKNOWN);
-
-        private final GHEvent event;
-        GitHubEventType(GHEvent event) {
-            this.event = event;
-        }
-
-        /**
-         * Required due to different naming conventions between different GitHub event names for Webhook events and
-         * GitHub events
-         *
-         * @param event
-         *            the github event as a string to convert to Event enum
-         * @return GHEvent
-         */
-        static GHEvent transformToGHEvent(@Nonnull String event) {
-            return EnumUtils.getEnumOrDefault(GitHubEventType.class, event, UnknownEvent).event;
-        }
-    }
 }