fix(parsers): gate rpm db impls by sqlite feature

[mstykow]

Summary

• make the RpmBdbDatabaseParser trait impls mutually exclusive across rpm-sqlite feature states
• restore the required PackageParser members on the non-rpm-sqlite impl to fix the --no-default-features build
• gate the SQLite-only path suffix constant so the non-SQLite build stays clean

Issues

• Covers: RPM DB parser feature-gating regression in src/parsers/rpm_db.rs

Scope and exclusions

• Included: one-file parser fix for cfg-gated trait impl completeness and SQLite-only constant gating
• Explicit exclusions: no parser behavior changes outside the cfg split, no assembly wiring changes, no documentation or fixture updates

Follow-up work

• Created or intentionally deferred: no blocking follow-up; five-agent review and focused local QA passed for default-feature and --no-default-features paths

Expected-output fixture changes

• Files changed: none
• Why the new expected output is correct: this fix only resolves a cfg-gated compile/trait-completeness issue and does not intentionally change parser output