[HUDI-4444] Refactor DataSourceInternalWriterHelper

[wombatu-kun]

Change Logs

DataSourceInternalWriterHelper constructor is writing files (through writeClient.startCommitWithTime and writeClient.preWrite), which is an anti-pattern.
Moved code that starts transaction (creates files through startCommitWithTime and preWrite) from constructor to separate method startTransaction() and called it from createInflightCommit().

Impact

none

Risk level (write none, low medium or high below)

none

Documentation Update

Describe any necessary documentation update if there is any new feature, config, or user-facing change

• The config description must be updated if new configs are added or the default value of the configs are changed
• Any new feature or user-facing change requires updating the Hudi website. Please create a Jira ticket, attach the ticket number here and follow the instruction to make changes to the website.

Contributor's checklist

• [ ] Read through contributor's guide
• [ ] Change Logs and Impact were stated clearly
• [ ] Adequate tests were added if applicable
• [ ] CI passed

[hudi-bot]

CI report:

• e2c574be3c2f8953e3973610fb0e20fef16f68ba Azure: SUCCESS

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