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
for (final JWK jwk : JwtRealmInspector.getJwksAlgsPkc(jwtRealm).jwks()) {
            logger.info("REALM PKC: jwk=[{}]", jwk);
        }
    }
    protected void printJwtIssuer(final JwtIssuer jwtIssuer) {
        logger.info(
            "ISSUER: iss=["
                + jwtIssuer.issuerClaimValue
                + "], aud=["
                + String.join(",", jwtIssuer.audiencesClaimValue)
                + "], principal=["
                + jwtIssuer.principalClaimName
                + "], algorithms=["
                + String.join(",", jwtIssuer.algorithmsAll)
                + "], httpServer=["
                + (jwtIssuer.httpsServer != null)
                + "]."
        );
        if (jwtIssuer.algAndJwkHmacOidc != null) {
            logger.info("ISSUER HMAC OIDC: alg=[{}] jwk=[{}]", jwtIssuer.algAndJwkHmacOidc.alg(), jwtIssuer.encodedKeyHmacOidc);
        }
        for (final JwtIssuer.AlgJwkPair pair : jwtIssuer.algAndJwksHmac) {
            logger.info("ISSUER HMAC: alg=[{}] jwk=[{}]", pair.alg(), pair.jwk());
        }
        for (final JwtIssuer.AlgJwkPair pair : jwtIssuer.algAndJwksPkc) {
            logger.info("ISSUER PKC: alg=[{}] jwk=[{}]", pair.alg(), pair.jwk());
        }
    }
}