Add type property to function nodes

[QMalcolm]

Resolves #12042
Resolves #12037

Problem

There are three distinct types of functions: scalar, aggregate, and table. We need to know which the user is specifying. Of note, the only built-in supported type in dbt-adapters currently is scalar.

Solution

• Add a type property to function nodes
• The type function node property supports values: scalar, aggregate, and `table
• The type function node property defaults to scalar if not explicitly specified

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]

Additional Artifact Review Required

Changes to artifact directory files requires at least 2 approvals from core team members.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (e949d1a) to head (8baf375).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12057      +/-   ##
==========================================
+ Coverage   91.87%   91.89%   +0.01%     
==========================================
  Files         203      203              
  Lines       24792    24802      +10     
==========================================
+ Hits        22778    22792      +14     
+ Misses       2014     2010       -4     

Flag	Coverage Δ
integration	88.78% <100.00%> (+0.02%)	⬆️
unit	65.21% <90.90%> (+0.01%)	⬆️

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Components	Coverage Δ
Unit Tests	65.21% <90.90%> (+0.01%)	⬆️
Integration Tests	88.78% <100.00%> (+0.02%)	⬆️

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