Update default stack version to 8.0.0

[mtojek]

This PR updates the default stack version to 8.0.0.

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-02-14T15:53:48.701+0000

• Duration: 28 min 37 sec

Test stats 🧪

Test	Results
Failed	0
Passed	524
Skipped	1
Total	525

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[mtojek]

Self-approved, we can review it later.

I need this one to check if #697 still works.

[jsoriano]

LGTM