[FEATURE] Set all macro namespace by default to ['<name_of_your_root_project>', '<macro_namespace>']

[JCZuurmond]

As suggested by @jtcohen6 in comment, change this

dbt-core/core/dbt/context/providers.py

Lines 146 to 147 in 280e9ad

	if not search_packages and namespace in self._adapter.config.dependencies:
	search_packages = [namespace]

to:

            if not search_packages and namespace in self._adapter.config.dependencies:
                search_packages = [self.config.project_name, namespace]

With this change, by default we prefer macro overwrites for packages (like spark__create_table_as) defined in the root project over the ones defined in the package. The user can change the preference behavior by defining the search order explicitly:

# dbt_project.yml
dispatch:
  - macro_namespace: dbt
    search_order: ['<package name>, '<root project name>']

In the old behavior the macros for packages in the root folder are not preferred over the ones in the packages, needing the user to explicitly set the search order to:

# dbt_project.yml
dispatch:
  - macro_namespace: dbt
    search_order: ['<root project name', '<package name>]

We think that the proposed change is a more sensible default.