Revert "[base] Use FuzzedDataProvider included in LLVM package."

This reverts commit 20d2671d9bb37c0545a39be4364134df1c19d44a.

Reason for revert: Causes build failures on iOS bots, see: https://crbug.com/999096

Original change's description:
> [base] Use FuzzedDataProvider included in LLVM package.
> 
> Bug: 991200
> Change-Id: Iee88e3a81057d509e18a2875a3070c5abc17c959
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1774303
> Auto-Submit: Max Moroz <mmoroz@chromium.org>
> Commit-Queue: Lei Zhang <thestig@chromium.org>
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#691207}

TBR=thestig@chromium.org,mmoroz@chromium.org

Change-Id: I044f8863f8fa7e2bb9e70b0f33e73fdd8bfa2a29
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 991200, 999096
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1776043
Reviewed-by: Oskar Sundbom <ossu@chromium.org>
Commit-Queue: Oskar Sundbom <ossu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691575}