Expose package iac/ folder and iac_blueprints in EPR

[bhapas]

Summary

Integrations will ship iac/ patches and materialized linked templates. EPR must serve those files when a package is pulled (GET /package/{name}/{version}/iac/... and the downloadable zip).

This PR:

• Confirms LoadAssets includes iac/ files in package assets (folder name has no hyphen, so it is not rejected).
• Relies on the existing static handler (GET /package/{name}/{version}/{name:.*}) and zip archiver (full directory walk) to serve and package iac/ content.
• Exposes iac_blueprints (and provider_permissions) on package / policy template / input / data stream JSON so Fleet/provisioner can discover patch metadata.

Related

• Relates to packages: expose iac_blueprints and provider_permissions in manifest structs #1888 (does not modify it)
• Companion package-spec: Add iac/ folder validation for JSON patches and linked base templates package-spec#1227
• Companion integrations: Add versioned root IaC blueprints and per-package iac patches/links integrations#20728

Test plan

Isolated tests in packages/iac_test.go use a temp-dir package (no testdata/package/ churn):

• TestPackageLoadAssetsIncludesIac — NewPackage + LoadAssets lists iac/account.cloudformation.patches.json and iac/account.cloudformation.json
• TestPackageIndexIncludesIaCBlueprints — package JSON includes iac_blueprints with id aws/federated-identity/account/v1
• TestServePackageResourceIac — ServePackageResource returns 200 + JSON body for the patches file
• TestArchivePackageIncludesIac — zip from ArchivePackage contains both iac/ files

go test ./packages/ ./archiver/ -count=1

[infra-vault-gh-plugin-prod]

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