Add object to context with compiled code for full refresh

[b-per]

Part of the solution to resolve dbt-labs/dbt-adapters#154

Needs to be released along with dbt-labs/dbt-adapters#900 for the materialization code.

Problem

Today it is not possible to set on_schema_change = full_refresh for incremental models.

Solution

To make it possible to add the feature, this implementation adds an object called sql_full_refresh to the context so that the materialization macros in dbt-adapters can use this variable.

This prevents having to re-compile the model if we realize that a model should run as a full refresh when its schema changes.

There is no test for now, but I am happy to add some if the approach in this PR along with the dbt-adapters one is OK to be merged.

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• 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.
• This PR includes type annotations for new and modified functions.

[github-actions]

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