JSpecify: Handle @Nullable elements for enhanced-for-loops on arrays

[armughan11]

Currently, enhanced-for-loops do not honor nullability annotations on arrays.

Current Behavior
Both these dereferences work fine.

static @Nullable String[] fizz = {"1"}
for (String s: fizz){
     s.toString();
     if (s!=null){
          s.toString();
     }  
}

New Behavior
The first one throws an error, as expected.

static @Nullable String[] fizz = {"1"}
for (String s: fizz){
     // BUG: Diagnostic contains: dereferenced expression s is @Nullable
     s.toString();
     if (s!=null){
          s.toString();
     }  
}

Fixes #983

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.95%. Comparing base (cc3dee3) to head (da98d36).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #986   +/-   ##
=========================================
  Coverage     85.94%   85.95%           
- Complexity     2069     2070    +1     
=========================================
  Files            83       83           
  Lines          6860     6863    +3     
  Branches       1318     1319    +1     
=========================================
+ Hits           5896     5899    +3     
  Misses          550      550           
  Partials        414      414           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[msridhar]

Overall LGTM! Just a couple of minor comments

[msridhar]

remove this whitespace change

[armughan11]

Fixed

[msridhar]

Thanks!