fix(indexer): capture Ruby module imports
Relates to gitlab-org/gitlab#600162. [skip schema-version-check] Wording-only change in the Extends edge description.
This MR is scoped to generic Ruby behavior: constants passed to include, extend, and prepend are indexed as imports, and mixin composition still uses the existing Extends edge.
I removed condition, policy, and GitLab *_mod_with handling from this MR. Those are framework/project macros and need opt-in macro support so they do not affect every Ruby project.
Test plan
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mise test:integration:codegraph -
mise lint:fmt - Commit hook: fmt and clippy
Edited by Michael Angelo Rivera