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 SecureString clientSecret = jwtAuthenticationToken.getClientAuthenticationSharedSecret();
            try {
                JwtUtil.validateClientAuthentication(
                    clientAuthenticationType,
                    clientAuthenticationSharedSecret,
                    clientSecret,
                    tokenPrincipal
                );
                logger.trace("Realm [{}] client authentication succeeded for token=[{}].", name(), tokenPrincipal);
            } catch (Exception e) {
                final String msg = "Realm [" + name() + "] client authentication failed for token=[" + tokenPrincipal + "].";
                logger.debug(msg, e);
                listener.onResponse(AuthenticationResult.unsuccessful(msg, e));
                return; 
            }
            final BytesArray jwtCacheKey = isCacheEnabled() ? new BytesArray(jwtAuthenticationToken.getUserCredentialsHash()) : null;
            if (jwtCacheKey != null) {
                final User cachedUser = tryAuthenticateWithCache(tokenPrincipal, jwtCacheKey);
                if (cachedUser != null) {
                    if (delegatedAuthorizationSupport.hasDelegation()) {
                        delegatedAuthorizationSupport.resolve(cachedUser.principal(), listener);
                    } else {
                        listener.onResponse(AuthenticationResult.success(cachedUser));
                    }
                    return;
                }
            }
            
            jwtAuthenticator.authenticate(jwtAuthenticationToken, ActionListener.wrap(claimsSet -> {
                if (logger.isDebugEnabled()) {