Change airbnb eslint config package to `eslint-config-airbnb-base` and update plugins.
Change `airbnb` to `airbnb-base` for .eslintrc `extends` value.
Added changelog entry
Made sure all plugins and envs are set
Corrected new failing specs
Create dynamic fixture for build_spec
## What does this MR do?
Replace `spec/javascripts/fixtures/build.html.haml` by a dynamically created fixture (using `rake teaspoon:fixtures`).
## Why was this MR needed?
The existing fixture was not representing the real page.
## What are the relevant issue numbers?
#24614 would have been avoided
following !6059
See merge request !7589
