feat: support lazy initialization of the SDK

[zhu-xiaowei]

Description

1. support lazy initialization of the SDK

General Checklist

• Added new tests to cover change, if needed
• Build succeeds using Swift Package Manager
• All unit tests pass
• 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

All modified and coverable lines are covered by tests ✅

Project coverage is 95.74%. Comparing base (a850795) to head (09af345).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #58      +/-   ##
==========================================
+ Coverage   95.66%   95.74%   +0.07%     
==========================================
  Files          35       35              
  Lines        1986     1999      +13     
==========================================
+ Hits         1900     1914      +14     
+ Misses         86       85       -1     

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