Add AWS Lambda/ECS/EKS methods to FIPS Compliance documentation

[misteriaud]

What does this PR do? What is the motivation?

This PR improves the FIPS Agent documentation and adds specific instructions for the supported installation methods.

Merge instructions

Merge readiness:

• [ ] Ready for merge

For Datadog employees: Merge queue is enabled in this repo. Your branch name MUST follow the <name>/<description> convention and include the forward slash (/). Without this format, your pull request will not pass in CI, the GitLab pipeline will not run, and you won't get a branch preview. Getting a branch preview makes it easier for us to check any issues with your PR, such as broken links.

If your branch doesn't follow this format, rename it or create a new branch and PR.

To have your PR automatically merged after it receives the required reviews, add the following PR comment:

/merge

Additional notes