Statsd tags

[joelmarty]

Fixes #105

Changes

• Bump com.datadoghq:java-dogstatsd-client to 4.0.0
• Pass tags to the statsd client instead of ignoring them
• Fix tests:
  • Move the StatsdAssertingUdpServer to the test sources
  • Expose the lines failing assertion: since the StatsdAssertingUdpServer runs in another thread, the exception was not picked up by JUnit and the test passed anyway.
  • Test the passed tags, which required to review the implementation and parse back the received metrics: the previous implementation ignored everything after the type field in the metric line.

[CLAassistant]

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