Add Windows/ECS/on-prem integration tests for OTLP, host_metrics, and Prometheus

[Paamicky]

Description of the issue

Integration testing gaps exist for OTel components publishing to the OTLP endpoint across multiple platforms. Specifically: Windows, on-prem, and ECS have no coverage for OTLP, Prometheus, or Host Metrics. Log and Traces have been added to the existing OTLP test (which was metrics only). Also, new features (root-level cluster_name, collection_interval standardization, Prometheus $1/${1} escape) need integration test coverage.

Description of changes

• Restructured otel_collect/ tests into linux/ and windows/ subdirectories for consistent platform organization
• Added Windows integration tests for OTLP, Host Metrics, and Prometheus using the validator pattern
• Added OTLP, Host Metrics, and Prometheus to on-prem (ec2_linux_onprem) test matrix
• Added OTLP, Host Metrics, and Prometheus to ECS (ecs_ec2_daemon) test matrix
• Updated all agent configs to include cluster_name and collection_interval for new feature validation
• Added $1 and ${1} relabel configs to Prometheus scrape configs to validate dollar escape handling
• Updated generator entries and partition exclusions to reflect new directory structure

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

• All generator code compiles
• All Linux test code compiles
• Tests cover: EC2 Linux, Windows, on-prem, ECS, and EKS (existing) platforms
• Features validated: OTLP endpoint publishing, cluster_name propagation, collection_interval, Prometheus $1/${1} escape
• integ test for PR scope: https://github.com/aws/amazon-cloudwatch-agent/actions/runs/29928201149/attempts/5
• integration test for full suite with PR: