Expand Test Coverage

[dehume]

Adding additional test coverage for:

• Cluster Replicas
• Clusters
• Databases
• Grants
• Grant Defaults
• Indexes
• Materialized Views
• Roles
• Schemas
• Secrets
• Tables
• Types
• Views
• Sources

Ensure that all resources have acceptance tests to cover all attributes for creation and modification within Terraform. Expanding unit tests for more complex resources based on tests from Materialize test drive. Also several updates to resources based on rereading documentation and looking at examples in Materialize tests:

• materialize_role
  [Breaking Change] Remove session_variables attribute. Being able to set this attribute is not helpful in the context of Terraform.

• materialize_table
  Allow default to be set for columns within a table.

• materialize_type
  Support the type of row.

• materialize_source_load_generator
  Include expose_progress attribute.

#374