### Description

The [Get API key information API](https://www.elastic.co/guide/en/elasticsearch/reference/master/security-api-get-api-key.html) can currently filter the returned keys by:
 * key id/name
 * keys owned by the calling user
 * keys owned by other users, by `realm_name` and `username`

Irrespective of the filtering used, both invalidated and expired (but not yet deleted) keys will be included in the response.
In the response, keys have the `invalidated` boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.

I propose we introduce a way for the API to support retrieving:
* only valid API keys (not return invalidated keys) - using a boolean request parameter
* keys not expired before a certain timestamp - using a timestamp parameter that defaults to "now" - also note that keys' experiation date is always checked against the local node's clock
x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ApiKeyService.java
}
    }
    /**
     * Gets the API Key from the <code>Authorization</code> header if the header begins with
     * <code>ApiKey </code>
     */
    ApiKeyCredentials getCredentialsFromThreadContext(ThreadContext threadContext) {
        if (false == isEnabled()) {
            return null;
        }
        return getCredentialsFromHeader(threadContext.getHeader("Authorization"), ApiKey.Type.REST);
    }
    static ApiKeyCredentials getCredentialsFromHeader(final String header, ApiKey.Type expectedType) {
        return parseApiKey(Authenticator.extractCredentialFromHeaderValue(header, "ApiKey"), expectedType);
    }
    public static String withApiKeyPrefix(final String encodedApiKey) {
        return "ApiKey " + encodedApiKey;
    }
    private static ApiKeyCredentials parseApiKey(SecureString apiKeyString, ApiKey.Type expectedType) {
        if (apiKeyString != null) {
            final byte[] decodedApiKeyCredBytes = Base64.getDecoder().decode(CharArrays.toUtf8Bytes(apiKeyString.getChars()));
            char[] apiKeyCredChars = null;
            try {
                apiKeyCredChars = CharArrays.utf8BytesToChars(decodedApiKeyCredBytes);
                int colonIndex = -1;
                for (int i = 0; i < apiKeyCredChars.length; i++) {
                    if (apiKeyCredChars[i] == ':') {
                        colonIndex = i;
                        break;
                    }