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
if (Strings.hasText(issuer) == false) {
            logger.warn("Issuer claim 'iss' is missing.");
            return new JwtAuthenticationToken("<unrecognized-jwt>", signedJWT, JwtUtil.sha256(userCredentials), clientCredentials);
        }
        
        for (Function<JWTClaimsSet, String> func : tokenPrincipalFunctions) {
            final String tokenPrincipalSuffix = func.apply(jwtClaimsSet);
            if (tokenPrincipalSuffix != null) {
                return new JwtAuthenticationToken(
                    issuer + "/" + tokenPrincipalSuffix,
                    signedJWT,
                    JwtUtil.sha256(userCredentials),
                    clientCredentials
                );
            }
        }
        
        
        return new JwtAuthenticationToken("<unrecognized-jwt> by " + issuer, signedJWT, JwtUtil.sha256(userCredentials), clientCredentials);
    }
    @Override
    public boolean supports(final AuthenticationToken jwtAuthenticationToken) {
        return (jwtAuthenticationToken instanceof JwtAuthenticationToken);
    }
    @Override
    public void authenticate(final AuthenticationToken authenticationToken, final ActionListener<AuthenticationResult<User>> listener) {
        ensureInitialized();
        if (authenticationToken instanceof JwtAuthenticationToken jwtAuthenticationToken) {
            final String tokenPrincipal = jwtAuthenticationToken.principal();