Revert "Reland "PreloadingDevTools: Disable prerendering for clients other than DevTools frontend""

This reverts commit b122b241.

Reason for revert: still suspect for flakes in prerender.js; see https://crbug.com/1465610

Original change's description:
> Reland "PreloadingDevTools: Disable prerendering for clients other than DevTools frontend"
>
> This reverts commit 1d662ac2.
>
> Original change's description:
> > Revert "PreloadingDevTools: Disable prerendering for clients other than DevTools frontend"
> >
> > This reverts commit 9d392f33.
> >
> > Reason for revert: Suspect for making
> > http/tests/inspector-protocol/tracing/prerender.js  flaky on Mac:
> > https://ci.chromium.org/ui/p/chromium/builders/ci/Mac10.15%20Tests
> > https://ci.chromium.org/ui/p/chromium/builders/ci/Mac10.15%20Tests/39245/overview
> >
> > Original change's description:
> > > PreloadingDevTools: Disable prerendering for clients other than DevTools frontend
> > >
> > > Prerendering introduced switching of FrameTreeNodes in the browser side
> > > and frame targets in the CDP client side. If a CDP client unaware of
> > > this logic and a prerendered page activated, it will cause unexpected
> > > behaviors. For example, Puppeteer loses control. To mitigate this, this
> > > CL disables prerendering if a target without tab target support is
> > > attached. For more details, see [1].
> > >
> > > [1] https://docs.google.com/document/d/12HVmFxYj5Jc-eJr5OmWsa2bqTJsbgGLKI6ZIyx0_wpA
> > >
> > > Bug: 1440085
> > > Change-Id: I80bf9234b60722112baf21c4fa2ee1f0d0cb3221
> > > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4495911


> > > Reviewed-by: Danil Somsikov <dsv@chromium.org>
> > > Commit-Queue: Ken Okada <kenoss@chromium.org>
> > > Cr-Commit-Position: refs/heads/main@{#1158723}
> >
> > Bug: 1440085, 1455943
> > Change-Id: I977f2a164081fdae5e7b54e4e8aa51088699280b
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4624573


> > Owners-Override: Christoph Schwering <schwering@google.com>
> > Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> > Auto-Submit: Christoph Schwering <schwering@google.com>
> > Reviewed-by: Christoph Schwering <schwering@google.com>
> > Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> > Cr-Commit-Position: refs/heads/main@{#1159585}
>
> Bug: 1440085, 1455943
> Change-Id: I18a9fea40f97162a70304dfa3d984ac51488f7be
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4686374


> Reviewed-by: Christoph Schwering <schwering@google.com>
> Commit-Queue: Ken Okada <kenoss@chromium.org>
> Reviewed-by: Danil Somsikov <dsv@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1170479}

Bug: 1440085, 1455943
Change-Id: I18f8b129cfd21f867494d4a9922182fee6db78dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4691027


Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Christoph Schwering <schwering@google.com>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1171406}