[SDTEST-116] Send event_created and event_finished metrics for internal telemetry

[anmarchenko]

What does this PR do? Adds event_created and event_finished metrics. As this PR is already large, I will implement other metrics in subsequent PRs.

Also this PR:

• only enables telemetry with Datadog Agent for now as agentless mode is not released yet in gem datadog
• refactors domain model code
• introduces telemetry helpers and constants
• bumps datadog dependency to 2.2 as this is currently the oldest version with metrics support
• adds minor changes to dev setup: run bundle in docker without bundler version, replace docker-compose command with docker compose command

How to test the change? Tested by running test suite with staging settings, see (DD only) dashboard here.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 99.41973% with 3 lines in your changes missing coverage. Please review.

Project coverage is 98.88%. Comparing base (03910f2) to head (afd50da).

Files	Patch %	Lines
spec/datadog/ci/test_visibility/component_spec.rb	92.00%	2 Missing :warning:
lib/datadog/ci/test_visibility/component.rb	98.63%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #200 +/- ## ========================================== + Coverage 98.86% 98.88% +0.01% ========================================== Files 235 242 +7 Lines 10477 10837 +360 Branches 481 489 +8 ========================================== + Hits 10358 10716 +358 - Misses 119 121 +2 ```

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