make SegmentInstant thread safe

[wenxi-zeng]

addressed threat safety concern mentioned in #200

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (fedb363) 83.61% compared to head (55d45bd) 78.54%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
...t/analytics/kotlin/core/utilities/DateTimeUtils.kt	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #207      +/-   ##
============================================
- Coverage     83.61%   78.54%   -5.08%     
  Complexity      495      495              
============================================
  Files            70       78       +8     
  Lines          5713     6586     +873     
  Branches        747      833      +86     
============================================
+ Hits           4777     5173     +396     
- Misses          298      739     +441     
- Partials        638      674      +36     

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