Fix compatibility with ElasticMQ

[Xnopyt]

This PR changes the Phlib\JobQueue\AwsSqs\JobQueue so it is compatible with ElasticMQ, which is a message queue server which is compatible with AWS SQS.

The only difference with ElasticMQ that seems to affect this library is that receiving from an empty queue will result in an empty $result['Messages'] array whereas AWS will not return the Messages property in the response at all. Funnily, this looks to be a better implementation of the AWS spec than AWS managed, as the spec specifies that the Messages array will always be in the response and does not mark it as optional.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.16%. Comparing base (ad4e670) to head (e89348f).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #19   +/-   ##
=========================================
  Coverage     69.16%   69.16%           
  Complexity      141      141           
=========================================
  Files            10       10           
  Lines           467      467           
=========================================
  Hits            323      323           
  Misses          144      144           

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