Migrate validate codeowners from datadog_checks_dev to ddev

[AAraKKe]

What does this PR do?

Migrates the validate codeowners command from datadog_checks_dev/.../tooling/commands/validate/codeowners.py to ddev/src/ddev/cli/validate/codeowners.py, rewrites the implementation to use ddev's Application output style and ddev modules, and ports the CodeOwners helper class out of tooling/codeowners.py into ddev/src/ddev/utils/codeowners.py. The legacy command file is deleted; the registry entry in tooling/commands/validate/__init__.py::ALL_COMMANDS is removed.

Helper gap notes

• tooling/codeowners.py::CodeOwners had no ddev equivalent. Ported to ddev/src/ddev/utils/codeowners.py with modernized type hints (list[...], tuple[...], X | None, Iterator). Unit tests added at ddev/tests/utils/test_codeowners.py.
• ddev/src/ddev/cli/ci/codeowners.py was the only other consumer of legacy tooling.codeowners. Its import was updated to the new ddev.utils.codeowners in this PR (call-out flagged in 02-validate-wave.md).
• tooling.utils.get_codeowners / get_codeowners_file / get_valid_integrations collapsed into inline private helpers. Path resolution uses app.repo.path / '.github' / 'CODEOWNERS'; integration enumeration uses app.repo.integrations.iter(['all']).
• tooling.constants.get_root → app.repo.path.
• tooling.commands.console.{abort, echo_failure, echo_success, annotate_error} → app.abort, app.display_error, app.display_success. ddev's Application does not surface a dedicated GitHub Actions annotation primitive; legacy annotate_error emitted an annotation alongside the same failure message, so dropping it does not change local behaviour. (Tracked separately: an app.annotate_* primitive will be added in a follow-up infrastructure PR; this command will be retrofitted then.)
• Repo type check (ctx.obj['repo_choice']) → app.repo.name. ddev's Application.set_repo normalises the same set of values (core / extras / marketplace / agent / local / env-driven).

Test plan

• ddev validate codeowners --help output unchanged from master
• ddev validate codeowners produces the same exit code (0) and substantive output ("All integrations have valid codeowners.") as master
• ddev --no-interactive test ddev -- -k codeowners passes (19/19)
• ddev --no-interactive test ddev passes (3 pre-existing GitHub VCR failures in tests/utils/test_github.py are unrelated; they stem from GitHubManager deriving the GitHub repo name from the local directory, which in a worktree named migrate-validate-codeowners produces requests against repos/DataDog/migrate-validate-codeowners instead of integrations-core and misses the recorded cassettes — fixed separately in a parallel infrastructure PR)

Motivation

Part of the datadog_checks_dev → ddev CLI migration wave (PR 1.3). Every CLI command currently registered in datadog_checks_dev's legacy tooling tree is being moved into ddev as native code, with the legacy tooling/ directory deleted at the end of the multi-phase migration. This PR ports validate codeowners and its supporting CodeOwners helper, removing one more dependency on the legacy CLI surface and freeing datadog_checks_dev to become a pure pytest plugin.

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

[github-actions]

⚠️ Major version bump
The changelog type changed or removed was used in this Pull Request, so the next release will bump major version. Please make sure this is a breaking change, or use the fixed or added type instead.

[codecov]

Codecov Report

❌ Patch coverage is 76.04790% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.84%. Comparing base (03b790e) to head (060b08b).

Additional details and impacted files

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[datadog-prod-us1-6]

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 76.05%
• Overall Coverage: 87.32% (+0.07%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 060b08b | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Validation Report

All 20 validations passed.

Show details

Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and Codecov settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

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