Add notificationConfigs for healthcare Hl7V2

[chrisst]

The healthcare API has deprecated a field at beta and removed it from the GA
launch of the api. In order to support this without having to duplicate the
entire resource this change supports defining a single field multiple times
with a different configruation for each version. Specifically it allows a field
to exist as deprecated at one version but not at another.
This also introduces the removed_message field.

This is another follow on to #3377 which GA'ed this resource without addressing the removed fields.

TODO - this change requires vendoring changes in both downstream repos.

Release Note Template for Downstream PRs (will be copied)

`google_healthcare_dataset` is now GA

`google_healthcare_dicom_store` is now GA

`google_healthcare_fhir_store` is now GA

`google_healthcare_hl7_v2_store` is now GA

`google_healthcare_dataset_iam_binding` is now GA

`google_healthcare_dataset_iam_member` is now GA

`google_healthcare_dataset_iam_policy` is now GA

`google_healthcare_dicom_store_iam_binding` is now GA

`google_healthcare_dicom_store_iam_member` is now GA

`google_healthcare_dicom_store_iam_policy` is now GA

`google_healthcare_fhir_store_iam_binding` is now GA

`google_healthcare_fhir_store_iam_member` is now GA

`google_healthcare_fhir_store_iam_policy` is now GA

`google_healthcare_hl7_v2_store_iam_binding` is now GA

`google_healthcare_hl7_v2_store_iam_member` is now GA

`google_healthcare_hl7_v2_store_iam_policy` is now GA

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 8 files changed, 153 insertions(+), 13 deletions(-))
Terraform Beta: Diff ( 8 files changed, 166 insertions(+), 11 deletions(-))
TF Conversion: Diff ( 1 file changed, 43 insertions(+))
TF OiCS: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 9 files changed, 154 insertions(+), 14 deletions(-))
Terraform Beta: Diff ( 9 files changed, 167 insertions(+), 12 deletions(-))
TF Conversion: Diff ( 2 files changed, 44 insertions(+), 1 deletion(-))
TF OiCS: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))