fix(runtime): process weak refs after manual gc

[andrewtdiz]

Summary

• treat WeakRef and FinalizationRegistry target slots as weak GC edges
• clear collected WeakRef targets and queue FinalizationRegistry cleanup jobs after explicit gc()
• add a regression covering WeakRef clearing, unregister suppression, and cleanup delivery

Tests

• cargo fmt --all --check
• CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-weakref-check cargo check -p perry-hir -p perry-codegen -p perry-runtime -p perry-stdlib
• CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build cargo build -p perry --release
• CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build cargo build -p perry-runtime -p perry-stdlib --release
• TMPDIR=/root/perry-worktrees/.tmp PERRY_GEN_GC=0 PERRY_NO_AUTO_OPTIMIZE=1 PERRY_RUNTIME_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build/release /root/perry-worktrees/.build-targets/perry-weakref-build/release/perry run test-files/test_issue_2656_weakref_finalization_gc.ts
• TMPDIR=/root/perry-worktrees/.tmp PERRY_GEN_GC=0 PERRY_NO_AUTO_OPTIMIZE=1 PERRY_RUNTIME_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build/release /root/perry-worktrees/.build-targets/perry-weakref-build/release/perry run test-files/test_gap_weakref_finalization.ts
• TMPDIR=/root/perry-worktrees/.tmp PERRY_GEN_GC=0 PERRY_NO_AUTO_OPTIMIZE=1 PERRY_RUNTIME_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build/release /root/perry-worktrees/.build-targets/perry-weakref-build/release/perry run test-files/test_issue_1766_weakref_internal_fields.ts
• TMPDIR=/root/perry-worktrees/.tmp PERRY_GEN_GC=0 PERRY_NO_AUTO_OPTIMIZE=1 PERRY_RUNTIME_DIR=/root/perry-worktrees/.build-targets/perry-weakref-build/release /root/perry-worktrees/.build-targets/perry-weakref-build/release/perry run test-parity/node-suite/globals/weakref-finalization-validation.ts