Add ingestion workflow logic

[vish-cs]

Code under workflow and Terraform folders is copied as-is from the data repo as part of the migration.
Changes are made to pom.xml and SpannerClient.java to read the schema file from the ingestion-helper.

[gemini-code-assist]

Code Review

This pull request implements a comprehensive import automation and Spanner ingestion pipeline. Key additions include Terraform configurations for GCP infrastructure, Cloud Workflows for process orchestration, and two Python-based helper services for managing ingestion tasks and Pub/Sub events. The code review identified several high-priority concerns, including a violation of the principle of least privilege in IAM role assignments and a security vulnerability in the JWT verification logic. Additionally, the reviewer noted the use of placeholder SQL in the aggregation utility, non-idiomatic flag parsing in Cloud Functions, and recommended enabling deletion protection for the Spanner database.