[feat] upgrading to flink 2.x

[goyal-anshul]

Why are the changes needed?

Close #171.

Brief change log

• Upgrading Flink from 1.19 to 2.1
• As part of the upgrade, some of the existing classes have been deprecated and removed. Adjusted all the breaking classes to their new counterpart in Flink 2.x.
• I kept the OutputFormat functionality as it is, to minimize the overall changes. As a result, I added a new method open() that does the same as the previous open(int, int) method. Since the OutputFormat interface is updated, I had to keep the method open(InitializationContext) but it is unused.

How was this patch tested?

I generated the jar file locally using mvn clean package. I then used the generated jar file in my local flink-sql pipeline for testing.

• Add some test cases that check the changes thoroughly including negative and positive cases if possible

• Add screenshots for manual tests if appropriate

• Run test locally before making a pull request

Documentation

• Does this pull request introduce a new feature? (yes / no): no
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[itinycheng]

I plan to merge the code first and will submit a PR later to fix the CI error.