Failed task signature on error handler

[nicklaros]

Current error handler only accept error as arguments, I propose to add failed task signature to make it more useful.
Some use case is when we need to broadcast error event about failed task to notify other system.

[nicklaros]

The documentation about Error Handling (https://github.com/RichardKnop/machinery#error-handling) suggest that it is used for handling task related error, so I think for broker.StartConsuming error, better not use the same error handler, so here I just log it instead.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 37.27%. Comparing base (260989d) to head (108d841).
⚠️ Report is 62 commits behind head on master.

Files with missing lines	Patch %	Lines
v2/worker.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #615      +/-   ##
==========================================
+ Coverage   37.24%   37.27%   +0.03%     
==========================================
  Files          36       36              
  Lines        3112     3109       -3     
==========================================
  Hits         1159     1159              
+ Misses       1805     1802       -3     
  Partials      148      148              

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