Fix handling of columns with Decimal data type in delta input source

[abhishekrb19]

The Delta Decimal type wasn't handled correctly in the Druid Delta connector, resulting in the error: Unsupported fieldType[Decimal(4, 2)] for fieldName[price].

There were no tests or existing tables with the Decimal type, so I've updated the existing table, complex-types-table to include this data type.

Note that the Decimal type can only be handled as a double at most in Druid. For a big decimal that cannot fit inside a double, it should be ingested as a string.

Release note

Fix handling of columns with Decimal data type in the delta input source.

• been self-reviewed.
• a release note entry in the PR description.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• been tested in a test Druid cluster.