perf(composer-repository): avoid redundant clones when checking security advisories

get_security_advisories cloned each package's full metadata blob
(hundreds of versions for popular packages) just to peek at its
"security-advisories" field. Same pattern already fixed in
load_async_packages by 2862d2da; move ownership through pattern
matches and IndexMap::shift_remove instead.

Measured with laravel/laravel create-project: response processing in
the security-advisories metadata branch drops ~80% (236ms -> 48ms),
and the whole run_security_advisory_filter phase drops from ~420-500ms
to ~250-270ms. End-to-end, shirabe now matches or edges out upstream
Composer (6.57s vs 6.85s in this run) instead of trailing by ~1.2s.

0 files changed, 0 insertions, 0 deletions