Port the Drupal 7 l10n_community test suite to 3.0.x functional tests

Problem/Motivation

The D7 branch has an end to end test class covering the welcome screen, listings, filters, lookups, warnings, suggestions, moderation and imports. The 3.0.x functional test is a stub, so none of those workflows are verified. Porting the D7 tests one to one gives 3.0.x a specification of what the D7 site does and shows where the port differs.

Steps to reproduce

Proposed resolution

Four ported classes mirroring the D7 methods step by step: welcome, languages and projects, suggestions, import. The already committed moderation test moves onto a shared base class, which builds the group type, language field and roles the module needs but does not ship, the D7 users, a Hungarian group, the team user, and releases from the potx test module through the parser's own callbacks, because the local package connector is a stub. Documented adaptations: group routes and field names, summaries and statistics placed as blocks, warnings read from the release page, two fewer strings from potx 8.x in the D7 test module, and the unreachable "No languages to list." state. One small code change rides along because the import test asserts it: the "successfully imported" message is back.

Remaining tasks

User interface changes

API changes

Data model changes