Add flags from dbt_project.yml to the Project and RuntimeConfig objects

[mikealfare]

Resolves #10618

Problem

We need to pass project flags from dbt_project.yml into the BaseAdapter instantiation to support behavior flags. Without this, users cannot override a behavior flag.

Solution

• add flags as an attribute on Project, which then adds it to RuntimeConfig
• pull the flags from dbt_project.yml::flags, not the global flags
  • the flags we're currently looking for are not expected to be overwritten by CLI args or environment variables
• ensure existing tests pass
• add tests that ensure RuntimeConfig contains arbitrary flags added in dbt_project.yml::flags

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]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.91%. Comparing base (2218140) to head (cc628f2).
Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10644      +/-   ##
==========================================
+ Coverage   88.86%   88.91%   +0.04%     
==========================================
  Files         180      180              
  Lines       22762    22799      +37     
==========================================
+ Hits        20228    20272      +44     
+ Misses       2534     2527       -7     

Flag	Coverage Δ
integration	86.16% <100.00%> (+0.05%)	⬆️
unit	62.36% <100.00%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	62.36% <100.00%> (+0.03%)	⬆️
Integration Tests	86.16% <100.00%> (+0.05%)	⬆️

[github-actions]

The backport to 1.8.latest failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.8.latest 1.8.latest
# Navigate to the new working tree
cd .worktrees/backport-1.8.latest
# Create a new branch
git switch --create backport-10644-to-1.8.latest
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 1d3d315249c81dbca70452e5a14fbfd0edad6b2a
# Push it to GitHub
git push --set-upstream origin backport-10644-to-1.8.latest
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.8.latest

Then, create a pull request where the base branch is 1.8.latest and the compare/head branch is backport-10644-to-1.8.latest.