Added dependency to swift-metrics

[ptoffy]

These changes are now available in 1.16.0

Added a dependency to swift-metrics to be able to record metrics on queues.

Metrics added:

• Timer to see how long a job takes to complete
• Counter to keep track of dispatched jobs
• Two different counters to keep track of successes and failures

[codecov]

Codecov Report

Attention: Patch coverage is 95.12195% with 2 lines in your changes missing coverage. Please review.

Project coverage is 84.48%. Comparing base (d867b5b) to head (aa9123e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/XCTQueues/TestQueueDriver.swift	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
+ Coverage   83.16%   84.48%   +1.32%     
==========================================
  Files          22       22              
  Lines         677      709      +32     
==========================================
+ Hits          563      599      +36     
+ Misses        114      110       -4     

Files with missing lines	Coverage Δ
Sources/Queues/AsyncQueue.swift	100.00% <100.00%> (ø)
Sources/Queues/Queue.swift	87.03% <100.00%> (+1.03%)	⬆️
Sources/Queues/QueueWorker.swift	96.66% <100.00%> (+1.21%)	⬆️
Sources/XCTQueues/TestQueueDriver.swift	90.00% <50.00%> (ø)

... and 1 file with indirect coverage changes

[0xTim]

Some points for discussion