Fix: Support dbt macro dispatch search order

[vchan]

This PR:

• Makes the dispatch mapping from a project config available to the adapter via jinja globals
• Updates the adapter's dispatch function to use search_order if configured
• Refactors prefix resolution

[Copilot]

Pull Request Overview

This pull request implements support for dbt macro dispatch search order, allowing projects to customize the order in which packages are searched when resolving macros through the adapter.dispatch() function.

• Adds support for the dispatch configuration in dbt_project.yml files
• Updates the adapter dispatch logic to respect custom search orders
• Adds comprehensive test fixtures and test cases to verify the functionality

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sqlmesh/dbt/package.py	Adds dispatch field to Package model and loads dispatch config from project YAML
sqlmesh/dbt/loader.py	Integrates dispatch configuration into the project loading process
sqlmesh/dbt/context.py	Adds dispatch storage and access methods to DbtContext
sqlmesh/dbt/adapter.py	Refactors dispatch method to use custom search orders from configuration
tests/dbt/test_adapter.py	Adds new test cases to verify dispatch search order functionality
Multiple test fixture files	Creates comprehensive test setup with packages, macros, and dispatch configuration

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[themisvaltinos]

why is the empty string needed? I might be wrong but also looking at the docs when dbt doesn't find either the adapter or namespace in dispatch it always falls back to default__ as prefix