[DOCS-14086] Add US2-FED (gov2) region to integration docs

[hestonhoffman]

Summary

• Adds gov2 (US2-FED) to site-region shortcode blocks in 4 integration README files: amazon_app_mesh, ecs_fargate, flink, openai

Context

US2-FED is a new Datadog GovCloud data center (IL5). The documentation repo PR (DataDog/documentation#36153) adds the new region across all site config and content. These integration READMEs are vendored into the docs repo and can only be updated from their upstream source.

Test plan

• Verify the generated docs pages for each integration render the correct site-region content when US2-FED is selected in the site selector

🤖 Generated with Claude Code

[dd-octo-sts]

⚠️ Recommendation: Add qa/skip-qa label

This PR does not modify any files shipped with the agent.

To help streamline the release process, please consider adding the qa/skip-qa label if these changes do not require QA testing.

[dd-octo-sts]

Validation Report

All 20 validations passed.

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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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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Use the US2-FED log intake host for gov2

When the site selector is US2-FED, adding gov2 to this gov block renders the FireLens example with the hard-coded US1-FED intake host (http-intake.logs.ddog-gov.datadoghq.com) instead of the US2-FED logs intake host (http-intake.logs.us2.ddog-gov.com). That sends ECS Fargate users selecting US2-FED to the wrong site; the same gov,gov2 pattern is repeated in the secret-based and CloudFormation FireLens snippets, so gov2 needs its own endpoint-specific block or a region-derived host.

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