Establish devfile naming convention for license requirements

What does this MR do and why?

This MR renames existing devfiles to indicate whether the resulting workspace is intended to be used with features outside the Free tier.

In order to use such a workspace in a meaningful way, setting GITLAB_ACTIVATION_CODE is required, but currently it is not visible which workspaces need this.

The renaming is a stop-gap for #551776 and further improvements on potential displaying additional information related to file names.

It was considered to instead create a subdirectory named ee, but this is currently not supported either.

References

gitlab-development-kit!4949 (merged)

How to set up and validate locally

1. Click on Code > Open in Workspace
2. Observe the dropdown for Devfiles contains the changed name now.

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