The logic for the cache in `JwtRealm` produces a broken `Cache` instance to some degree. 
We create a `BytesArray` from the user credential hash:

```java
            final BytesArray jwtCacheKey = isCacheEnabled() ? new BytesArray(jwtAuthenticationToken.getUserCredentialsHash()) : null;
            if (jwtCacheKey != null) {
                final User cachedUser = tryAuthenticateWithCache(tokenPrincipal, jwtCacheKey);
```

and use it as as a cache key in a `Cache` instance down the line.
But then we also clear the bytes in that `BytesArray` to `0` in org.elasticsearch.xpack.security.authc.jwt.JwtAuthenticationToken#clearCredentials. 

This leads to the hash map in the `Cache` getting filled with loads of `BytesArray` that all have the same 0-filled content but that were not equal to each other when first inserted into the map, causing the map to put them all in the same bucket.

<img width="1233" alt="image" src="https://github.com/elastic/elasticsearch/assets/6490959/86a914d7-a2d4-4b01-ad99-e0d14e71a58b">

ref path to the broken map:

<img width="1436" alt="image" src="https://github.com/elastic/elasticsearch/assets/6490959/87ac6f78-bc09-41c4-9a79-28fbbd14f6e6">

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/jwt/JwtRealm.java
final String msg = "Realm [" + name() + "] does not support AuthenticationToken [" + className + "].";
            logger.trace(msg);
            listener.onResponse(AuthenticationResult.unsuccessful(msg, null));
        }
    }
    void ensureInitialized() {
        if (delegatedAuthorizationSupport == null) {
            throw new IllegalStateException("Realm has not been initialized");
        }
    }
    
    RealmConfig getConfig() {
        return config;
    }
    
    JwtAuthenticator getJwtAuthenticator() {
        return jwtAuthenticator;
    }
    private User tryAuthenticateWithCache(final String tokenPrincipal, final BytesArray jwtCacheKey) {
        final ExpiringUser expiringUser = jwtCache.get(jwtCacheKey);
        if (expiringUser == null) {
            logger.trace("Realm [" + name() + "] JWT cache miss token=[" + tokenPrincipal + "] key=[" + jwtCacheKey + "].");
        } else {
            final User user = expiringUser.user;
            final Date exp = expiringUser.exp; 
            final String principal = user.principal();
            final Date now = new Date();
            final boolean cacheEntryNotExpired = now.getTime() < exp.getTime();
            logger.trace(
                "Realm [{}] JWT cache {} token=[{}] key=[{}] principal=[{}] exp=[{}] now=[{}].",