Improve third-party NTPs creation performance by using spare renderer

The current implementation of the third-party NTPs in the browser does
not make use of the spare renderer. As a result, third-party search
engine NTPs that depend on the current architecture experience delays
because they have to create a new process rather than reusing an
existing spare renderer.

This change primarily updates three parts. First, we have to late-bind
the instant process flag. Currently, the flag is passed as a
command-line switch when the process is created, which prevents spare
renderers from attaching the instant process flag as spare renderers
doesn't know if it's instant process at that moment. To address this
issue, we introduce a new method, SetConfigurationOnProcessLockUpdate(),
in the existing RendererConfiguration mojom interface. This method is
called in NotifyRendererOfLockedStateUpdate() to late bind the instant
process flag when process lock is updated. Additionally, we reuse
process_state.cc to store and expose the instant process setting.

The 2nd part of the change aims to enable the instant process to utilize
the spare renderer. We introduced a feature flag,
kInstantUsesSpareRenderer, to serve as the experimental control flag.
Additionally, we updated ChromeContentBrowserClient::IsSuitableHost() to
bypass the check if the spare renderer is taken by the instant process.
We made this change because InstantService::AddInstantProcess is called
after RenderProcessHostImpl::MayReuseAndIsSuitable() check in
RenderProcessHostImpl::GetProcessHostForSiteInstance(), which could hit
the "Unsuitable process reused for site" NOTREACHED.

The third part is to ensure that the renderer security settings are
passed to the process in time, before the renderer thread is created.
However, the order of mojo calls is not guaranteed on non-associated
interfaces in service worker cases. Therefore, we add
WaitForProcessReady() to make the service worker creation thread wait
until the renderer configuration (instant flag) and other
security-related settings are set before attempting to create the
worker.

Bug: 398159675
Change-Id: Ib7c3a7ca1bedae9174cd415e313ef43cfaf06b7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6373046
Commit-Queue: Wangsong Jin <wangsongjin@microsoft.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: Shunya Shishido <sisidovski@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1501448}