We somehow forgot to thread through the VectorSlotPair for the CALL_IC
based speculation feedback to CheckedTaggedToTaggedPointer. This was
showing for example with `String#concat()` where we ended up with an
endless deoptimization loop if the parameter was a Smi.

Bug: v8:8913
Change-Id: I84d90403f6fada9b435d4eb71c689edc3c34dc86
Reviewed-on: https://chromium-review.googlesource.com/c/1488770
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59871}