Update 'Build Custom Ingestion Pipeline' sample code to use more CDP

[sreuland]

What problem does your feature solve?

the current sample code for Build Custom Ingestion Pipeline uses existing captive core and horizon ingest sdk. It doesn't use newer CDP pre-computed tx meta and functional transforms, nor does it show how the migration path from that to CDP would look.

What would you like to see?

Add a migration guide/step to Build Custom Ingestion Pipeline that demonstrates how to migrate the existing ingestion code based on captive-core/horizon over to CDP SDK approach.
Retain the current example code as-is and show a second example code which highlights creating two pipelines of a CDP:

• CDP Origin Pipeline, demonstrate Galexie export instead of captive core for how to build a datastore GCS bucket.
• CDP Transform pipeline, demontrate how to derive a sample data model such as payment, this pipeline uses the GCS Bucket as origin and then applies functional operators to transform the network data into the derived payment model.

Blocked by: go/5412 , go/5413

What alternatives are there?