[Bugfix] Support "starrocks.filter.query" for Spark SQL read

[feihengye]

What type of PR is this：

BugFix

Which issues of this PR fixes ：

Fixes #91

Problem Summary(Required) ：

[CLAassistant]

All committers have signed the CLA.

[banmoy]

Thanks for the PR. I think it's ok to support user-defined filters in the configuration. Just curious about why not add filter in the join clause like
select * from spark_starrocks_4 a join spark_starrocks_4 b on a.name = b.name where a.name = 'jhon' or a.name = 'Lucy'
The filter will be pushed down to the source automatically, and it seems more flexible. Defining the filter in the configuration is generally used for DataFrame program.

[banmoy]

1. what if the user configures the filter, but the framework's filters is null?
2. add a test to verify it. please refer to ReadWriteITTest#testSql for an example.

[feihengye]

1. use old config, ConfigurationOptions.STARROCKS_FILTER_QUERY
2. ok

[banmoy]

Please deal with the DCO and CLA check failure

[feihengye]

Thanks for the PR. I think it's ok to support user-defined filters in the configuration. Just curious about why not add filter in the join clause like select * from spark_starrocks_4 a join spark_starrocks_4 b on a.name = b.name where a.name = 'jhon' or a.name = 'Lucy' The filter will be pushed down to the source automatically, and it seems more flexible. Defining the filter in the configuration is generally used for DataFrame program.

Thanks for you answer.
User create tmp view and config the push down filters already， it is a table now. And I want to push down filters to the table.

[banmoy]

LGTM. Thanks.