Add support for Iceberg Table Materialization

[VersusFacit]

resolves: #321

Add support for Iceberg Table Materialization

Built atop jaffle shop classic for testing.

Problem

We want to add support for materialization S3 bucket Iceberg tables in Snowflake.

Example of our decided model config interface:

{{
  config(
    materialized = "table",
    table_format="iceberg",
    external_volume="s3_iceberg_snow",
    base_location="milas_working_folder",
  )
}}
-- transient gets auto-`falsed`
-- `transient=true` is ignored
select * from {{ ref('raw_orders') }}

Solution

• Precisely insert additional Iceberg DDL into existing table materialization
• load all custom logic possible into Python
• manually attach is_iceberg as a field to show objects (this will be given to us by Snowflake for free one day)
• use is_iceberg to determine drop_relation_if_exists calls before building a table (table -> Iceberg, Iceberg -> table)
• gatekeep behind a behavior flag for those who have no need of Iceberg format tables!

Caveats

this is ready for review but needs two more things I can identify:

1. a behavior flag to gate Iceberg (did we merge that capability yet?)
2. activate tests (but while we have an Iceberg volume on our team cluster, it doesn't seem it's live yet on the CI one here)

Impact

Get this shipped for Cloud folks to start using!!

Manually testing scenarios

• [x] build an Iceberg table that refs a table
• [x] build an iceberg table on top of a table
• [x] seamless creates from table to iceberg table and back
• [x] did stress tests to confirm memory usage / time tradeoff of left join with show objects was worth it
• [x] a complex config model, with cluster by and iceberg at the same time

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have run this code in development and it appears to resolve the stated issue
• [x] (well, err, sort of) edit: Now, this PR includes tests, or tests are not required/relevant for this PR
• [x] This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions[bot]]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-snowflake contributing guide.

[VersusFacit]

Blocked by behavior flag / Jinja security issue. Once we have a solution forward, this PR is ready for code review round 2!