MONGOID-5069: fix Mongoid::Matcher.extract_attribute() for numeric Hash keys inside expanded array

[dalton-braze]

Summary

Mongoid::Matcher.expand_attribute() did not correctly handle numeric hash keys inside expanded arrays. This PR provides the fix + test cases.

Test Output (No Changes)

% rake spec

  1) Matcher.extract_attribute traversal.yml numeric Hash key inside expanded array has the expected exists flag
     Failure/Error: actual[0].should == expected_exists
     
       expected: true
            got: false (using ==)
       Diff:
       @@ -1 +1 @@
       -true
       +false
                                                                                                                        
  2) Matcher.extract_attribute traversal.yml numeric Hash key inside expanded array has the expected value
     Failure/Error: actual[1].should == expected_value

       expected: [3]
            got: nil (using ==)
                                                                                                                                             
  3) Matcher.extract_attribute traversal.yml multiple numeric Hash keys inside expanded array has the expected exists flag
     Failure/Error: actual[0].should == expected_exists

       expected: true
            got: false (using ==)
       Diff:
       @@ -1 +1 @@
       -true
       +false
                                                                                                                                                 
  4) Matcher.extract_attribute traversal.yml multiple numeric Hash keys inside expanded array has the expected value
     Failure/Error: actual[1].should == expected_value
     
       expected: [5, 6]
            got: nil (using ==)

XYZ examples, 4 failures

Test Output (Fix Implemented)

XYZ examples, 0 failures

[p-mongo]

This is fixed in #4980.