fix(flow)!: sliding window blocks until the first window is elapsed

[reugn]

• Replace NewSlidingWindowWithExtractor with NewSlidingWindowWithOpts which takes multiple configuration options.
• Introduce a configuration option for partial results, addressing the issue where the flow blocks until the first window is elapsed even if the upstream has closed.
• Replace return type for event type extractor from int64 to time.Time.
• Optimize windowing process.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.57%. Comparing base (683f3f7) to head (ce68e9a).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #165   +/-   ##
=======================================
  Coverage   99.57%   99.57%           
=======================================
  Files          12       12           
  Lines         699      707    +8     
=======================================
+ Hits          696      704    +8     
  Misses          3        3           

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