This reverts commit 8ff8ddba.

Reason for revert: Causes failures on GC Stress and TSan:

https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20gc%20stress/24138
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20TSAN/27969

Original change's description:
> [turbofan] Further brokerize BytecodeGraphBuilder
> 
> Replace all usages of VectorSlotPair with FeedbackSource.
> 
> Bug: v8:7790
> Change-Id: I0ac6e9cd8f5730154cc1842e267ca1ebfdebc874
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1763536
> Commit-Queue: Maya Lekova <mslekova@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63378}

TBR=neis@chromium.org,mslekova@chromium.org

Change-Id: Ieb6fb24dd0626fd9eb2183844614ac5b3c8084e8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7790
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1769287Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63387}