Ignore field.length validation for Named aggregation SHARD_ID column

[niveathika]

Purpose

$subject as this column is injected by the Named aggregation implementation.

Goals

To suppress 'field.length' validation for columns introduced by the aggregations, since SHARD_ID column is only present when distributed aggregation is enabled.

Approach

Ignore validation if field.length contains SHARD_ID config

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? yes
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes