Tests - Add embed base layers in the test project

[Gustry]

Backport of #4846

[3liz-bot]

The backport to release_3_7 failed:

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

stderr

error: could not apply b79cbb355... Tests - Add embed base layers in the test project
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config advice.mergeConflict false"

stdout

Auto-merging tests/units/classes/Project/ProjectTest.php
CONFLICT (content): Merge conflict in tests/units/classes/Project/ProjectTest.php

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-release_3_7 release_3_7
# Navigate to the new working tree
cd .worktrees/backport-release_3_7
# Create a new branch
git switch --create backport-4848-to-release_3_7
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick b79cbb3550a3a4774824959d81e9f580696c33e6,a11bcb2bc1e203d2d0dd794badb968ecfc32574a,5a3eed469050357920ec179bd6d7d70eb275f007
# Push it to GitHub
git push --set-upstream origin backport-4848-to-release_3_7
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release_3_7

Then, create a pull request where the base branch is release_3_7 and the compare/head branch is backport-4848-to-release_3_7.