Use the FSEvents API as the default on Mac

[sungshik]

This PR sets the default backend on Mac to the native FSEvents API (as already documented in the README).

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.6%. Comparing base (ce46e33) to head (13f4a50).

Files with missing lines	Patch %	Lines
...ava/engineering/swat/watch/impl/jdk/JDKPoller.java	0.0%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #54     +/-   ##
=========================================
- Coverage     81.9%   81.6%   -0.4%     
+ Complexity     166     164      -2     
=========================================
  Files           23      23             
  Lines          827     828      +1     
  Branches        97      97             
=========================================
- Hits           678     676      -2     
- Misses          90      92      +2     
- Partials        59      60      +1     

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