Dataset access viewer is primitive role READER not VIEWER

[slevenick]

Fixes: hashicorp/terraform-provider-google#6425

Added a test for this role as well

Release Note Template for Downstream PRs (will be copied)

bigquery: Fixed an issue with `google_bigquery_dataset_access` failing for primitive role `roles/bigquery.dataViewer`

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 2 files changed, 17 insertions(+), 5 deletions(-))
Terraform Beta: Diff ( 2 files changed, 17 insertions(+), 5 deletions(-))