Add state metric to windows services

[briantu]

What does this PR do?

Added a new windows_service.state metric which always emits 1 and is tagged with windows_service_state. This allows the user to create timeseries graphs that can filter the windows services by state.

Motivation

https://datadoghq.atlassian.net/browse/WINA-2011

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

❌ Patch coverage is 95.12195% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.00%. Comparing base (1dc27b5) to head (e720e31).
⚠️ Report is 30 commits behind head on master.

Additional details and impacted files

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[github-actions]

⚠️ The qa/skip-qa label has been added with shippable changes

The following files, which will be shipped with the agent, were modified in this PR and
the qa/skip-qa label has been added.

You can ignore this if you are sure the changes in this PR do not require QA. Otherwise, consider removing the label.

List of modified files that will be shipped with the agent

windows_service/changelog.d/21830.added
windows_service/datadog_checks/windows_service/windows_service.py