refactor(config): rename devModules to buildModules

[pi0]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

devModules, initially introduced by #5102 to have a way to only include some modules during dev/build time and removing from production dependencies at runtime. It was named after devDependencies section in package.json as such modules should not be installed for production environment at all. However the original name is proven to be little confusing and making users thinking it is only for development time. New buildModules name tries to make it more clear.
However devModules was not documented, backward compatibility with deprecation massage is added to support devModules until 3.x.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

updated

[manniL]

Great! It's important that we can somehow track the legacy fallbacks we have to remove for Nuxt 3, so adding it in the error message or as a TODO is the best way (to easily grep them out) IMO ☺️

[pi0]

@manniL Good idea. I believe we can do this for all parts in a separate chore PR.