Add role arn

[modular-magician]

Adds the option to use role_arn for the transfer service resource. Fixes hashicorp/terraform-provider-google#10880.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.

I did generate this and make sure it could build. make test and make lint didn't do anything because there was no rule for the make target.

• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).

Looks like S3 sources aren't supported in the third party tests. Probably because it would require infrastructure to create resources in AWS S3?

• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).

There aren't any relevant tests as far as I know.

• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

storage: added field `transfer_spec.aws_s3_data_source.role_arn` to `google_storage_transfer_job`

Derived from GoogleCloudPlatform/magic-modules#5619