The original CL title was updated to reflect CL contents. The
--win64-unwinding-info flag still exists but it is set by default.

This is a reland of efd8c2d9

Original change's description:
> Remove --win64-unwinding-info flag and always generate unwind info on Win/x64
>
> The generation of unwind info to enable stack walking on Windows/x64
> (https://chromium-review.googlesource.com/c/v8/v8/+/1469329) was implemented
> behind a temporary flag, in order to coordinate these changes with the
> corresponding changes in Chromium.
>
> The required changes to Chromium
> (https://chromium-review.googlesource.com/c/chromium/src/+/1474703) have also
> been merged, so we can now remove the flag and enable the generation of stack
> unwinding info by default on Windows/x64.
>
> Bug: v8:3598
> Change-Id: I88814aaeabecc007f5262227aa0681a1d16156d5
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1573138
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Paolo Severini <paolosev@microsoft.com>
> Cr-Commit-Position: refs/heads/master@{#61020}

Bug: v8:3598, chromium:958035
Change-Id: Ie53b39f3bb31567797a61e5110685284c266c1f9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1599596
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61368}