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/test/java/org/elasticsearch/xpack/security/authc/jwt/JwtRealmTestCase.java
if (randomBoolean()) {
            
            authcSettings.put(RealmSettings.getFullSettingKey(authcRealmName, JwtRealmSettings.POPULATE_USER_METADATA), randomBoolean());
        }
        if ((authzRealmNames.length != 0) || (randomBoolean())) {
            
            authcSettings.put(
                RealmSettings.getFullSettingKey(authcRealmName, DelegatedAuthorizationSettings.AUTHZ_REALMS.apply(JwtRealmSettings.TYPE)),
                String.join(",", authzRealmNames)
            );
        }
        
        if (randomBoolean()) {
            authcSettings.put(
                RealmSettings.getFullSettingKey(authcRealmName, JwtRealmSettings.JWT_CACHE_TTL),
                randomIntBetween(10, 120) + randomFrom("s", "m", "h")
            );
        }
        authcSettings.put(RealmSettings.getFullSettingKey(authcRealmName, JwtRealmSettings.JWT_CACHE_SIZE), jwtCacheSize);
        
        final MockSecureSettings secureSettings = new MockSecureSettings();
        if (jwtIssuer.algAndJwksHmac.isEmpty() == false) {
            secureSettings.setString(
                RealmSettings.getFullSettingKey(authcRealmName, JwtRealmSettings.HMAC_JWKSET),
                jwtIssuer.encodedJwkSetHmac
            );
        }
        if (jwtIssuer.encodedKeyHmacOidc != null) {
            secureSettings.setString(
                RealmSettings.getFullSettingKey(authcRealmName, JwtRealmSettings.HMAC_KEY),