feat: Add FIPS layers to layers-gov.json

[lym953]

What does this PR do?

1. In generate_layers_json.sh, add layer names Datadog-Extension-FIPS and Datadog-Extension-ARM-FIPS so the FIPS layers for GovCloud can be added to layers-gov.json
2. Reformat the lists LAYER_NAMES and JSON_LAYER_NAMES. Make each value have a single line for better readability.

Motivation

This is the first step towards supporting FIPS in Serverless Plugin.

Testing Guidelines

Run aws-vault exec sso-govcloud-us1-fed-engineering -- ./scripts/generate_layers_json.sh -g, which updates layers-gov.json.

Additional Notes

The next PR will add a parameter to allow choosing the FIPS layer.

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog