fix: change user engagement event and engagement time calculate rule

[zhu-xiaowei]

Description

Change the user engagement event definition to: Calculate an engagement event for each screen leave.
Changes the screen view engage time to the engage time of the previous user engagement event.
Add configuration for user engagement event.

General Checklist

• Added new tests to cover change, if needed
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (1d54f80) 100.00% compared to head (9f7898c) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #13   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           24        24           
  Lines          928       950   +22     
  Branches       168       173    +5     
=========================================
+ Hits           928       950   +22     

Files Changed	Coverage Δ
src/provider/Event.ts	100.00% <ø> (ø)
src/types/Analytics.ts	100.00% <ø> (ø)
src/provider/AnalyticsEventBuilder.ts	100.00% <100.00%> (ø)
src/provider/ClickstreamProvider.ts	100.00% <100.00%> (ø)
src/tracker/PageViewTracker.ts	100.00% <100.00%> (ø)
src/tracker/SessionTracker.ts	100.00% <100.00%> (ø)
src/util/StorageUtil.ts	100.00% <100.00%> (ø)

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