[HUDI-6218] Support instant_time/commit_time of savepoint procedure optional

[SteNicholas]

Change Logs

Procedure parameter instant_time/commit_time of savepoint procedure optional could be optional and uses the latest instant when the value of instant_time/commit_time is null or empty.

Impact

Support instant_time/commit_time of savepoint procedure including create_savepoint, delete_savepoint and rollback_to_savepoint optional.

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

[SteNicholas]

@yihua, @XuQianJin-Stars, @xiarixiaoyao, PTAL.

[hudi-bot]

CI report:

• cb4f488 Azure: SUCCESS

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