KSQL-12911 | Transform to Process Migration (2nd PR)

[hrishabhg]

Description

KStream has removed transform and deprecated transformValues and requires their usage to be replaced with processor api's process and processValues.

Current PR contains the following changes

• Simplified KSqlTransformer by removing ProcessingContext. It has no usage from transformation perspective.
• Implementation of KsProcessor and KsFixedKeyProcessor to replace stream.transform and stream.transformValues. Note: ktable.transform and equivalents have not been deprecated yet.

Testing done

• Unit Tests
• Integration Tests

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")
• Do these changes have compatibility implications for rollback? If so, ensure that the ksql command version is bumped.

[confluent-cla-assistant]

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