ADAP-1123: Create the package subdirectory

[mikealfare]

Problem

We need to move files into a package sub-directory to prepare for merging into the monorepo. This needs to be done in such a way that existing pull requests can be rebased against monorepo/stage to pick up those file migrations.

Solution

• use git mv when moving files or directories to pick up those file migrations in git history
• update workflows to reference the new sub-directory where applicable
• verify a branch created off of main can be rebased on monorepo/stage

I tested this by:

• create a branch off of main (called test for reference here)
• make updates to a method in PostgresAdapter
• make updates to a macro
• commit these changes in test
• rebase test onto monorepo/subpackage-namespace (this branch)
• observe that the changes occurred as expected, in the moved files, leaving no orphan files behind
• ensuring the CI still passes given the new workflows

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/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

[colin-rogers-dbt]

tallyho