Add data source for getting a list of Cloud Credentials

[chris-ackerman-dentsu]

Add a new data source to list all Cloud Credentials in the org.
This should provide a list of all the credential names in a given Org filtered by a credential type.

This list should be able to be used to create a credential data source based on the names returned.

Usage example:

data "env0_cloud_credentials" "azure_deployment_credentials" {
credential_type = "AZURE_SERVICE_PRINCIPAL_FOR_DEPLOYMENT "
}

data "env0_azure_credentials" "azure_deployment_credentials" {
for_each = toset(data.env0_cloud_credentials.azure_deployment_credentials.names)
name = each.value
}

Relevant API:
https://developer.env0.com/docs/api/b3A6ODc4NjAxMA-list-organization-credentials