SQL Client should support HTTPS with built-in JDK certificates

Related to FLINK-32030 

Internally SQL Client uses  Flink’s RestClient [1].  This client decides whether to enable SSL not on the basis of the URL schema ([https://|https:]...), but based on Flink configuration, namely a global security.ssl.rest.enabled  parameter [2] (which is also used for the REST server-side configuration ). When this parameter is set to true, it automatically requires user-supplied  security.ssl.rest.truststore  and security.ssl.rest.keystore to be configured - there is no default option to use certificates from JDK. After URL support for SQL Client gateway mode (FLINK-32030) gets added, the SQL Client should automatically use certificates built in into the JDK unless user-supplied trust- and keystores are configured. 

[1] https://github.com/apache/flink/blob/5dddc0dba2be20806e67769314eecadf56b87a53/flink-table/flink-sql-client/src/main/java/org/apache/flink/table/client/gateway/ExecutorImpl.java#L359
[2] https://github.com/apache/flink/blob/5d9e63a16f079399c6b51547284bb96db0326bdb/flink-runtime/src/main/java/org/apache/flink/runtime/rest/RestClientConfiguration.java#L103