Revert of [Compiler] Track Ignition background compilation separately in RuntimeStats. (patchset #3 id:80001 of https://codereview.chromium.org/2577263002/ )

Reason for revert:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/13358

Original issue's description:
> [Compiler] Track Ignition background compilation separately in RuntimeStats.
>
> Tracks background compilation of Ignition in a separate bucket from main thread
> compilation. Also add some more compilation buckets for functions which can take a
> significant proportion of compilation.
>
> BUG=v8:5203,v8:5215
>
> Review-Url: https://codereview.chromium.org/2577263002
> Cr-Commit-Position: refs/heads/master@{#42026}
> Committed: https://chromium.googlesource.com/v8/v8/+/b0e9116d59326a4f9a4f4691b61a510e342338c9

TBR=jochen@chromium.org,cbruni@chromium.org,rmcilroy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5203,v8:5215

Review-Url: https://codereview.chromium.org/2609773003
Cr-Commit-Position: refs/heads/master@{#42031}