Reland "mac: Forcibly disable Apple’s “Probabilistic Guard Malloc”"

This reverts commit ee6030a99cc6044f3e88be52d65d23ed605f9952.

Reason for revert: Relanding with a speculative fix for whatever went
wrong on the mac64 bot. 14 tests in interactive_ui_tests began failing
consistently on that bot when this initially landed
(https://ci.chromium.org/ui/p/chrome/builders/ci/mac64/228377), and they
recovered when this was reverted
(https://ci.chromium.org/ui/p/chrome/builders/ci/mac64/228421). I was
unable to reproduce those failures locally or in try jobs. I did
experience a different set of interactive_ui_tests failures on
mac_chromium_dbg_ng
(https://ci.chromium.org/ui/p/chromium/builders/try/mac_chromium_dbg_ng/2711),
and those failures persist with this updated patch with the speculative
fix
(https://ci.chromium.org/ui/p/chromium/builders/try/mac_chromium_dbg_ng/2712),
but those test failures seem to appear on that bot whenever it runs
interactive_ui_tests
(https://ci.chromium.org/ui/p/chromium/builders/try/mac_chromium_dbg_ng/2700).

The speculative fix is to set environment variables via LSEnvironment in
Info.plist only for the browser .app. LSEnvironment is removed from the
helper .app’s Info.plist. The thought is that interactive_ui_tests runs
out of its own executable and not the browser .app, but does use the
helper .app. By not setting MallocProbGuard=0 for the helper .app, it
should experience no changes when running under interactive_ui_tests.
Meanwhile, when running normally, MallocProbGuard=0 will be set in the
environment even for helper processes by virtue of running as children
of the browser process, which runs out of the browser .app whose
Info.plist still contains LSEnvironment.

MallocNanoZone is also removed from helper apps’ Info.plists according
to the same logic.

PWA stub .apps also retain LSEnvironment, because they are launched
directly by users as the browser .app, and should follow the same logic.

Original change's description:
> Revert "mac: Forcibly disable Apple’s “Probabilistic Guard Malloc”"
>
> This reverts commit 340be9daf6487e9ead5565f74543cde8bdfc3aac.
>
> Reason for revert: Suspicious for causing consistent test failures on mac64 builder
> i.e. https://ci.chromium.org/ui/p/chrome/builders/ci/mac64/228377/overview
>
> Bug: 414750473
> Original change's description:
> > mac: Forcibly disable Apple’s “Probabilistic Guard Malloc”
> >
> > “Probabilistic Guard Malloc” is normally disabled for non-Apple
> > executables when not running on Apple-internal OS builds. When
> > restarting Chrome from the macOS-provided “quit unexpectedly” dialog
> > after a browser crash, this malloc feature will be enabled, as observed
> > on macOS 15.4.1. Code inspection shows that this may be a new behavior
> > in macOS 15.3, although this is not dispositive, because only libmalloc
> > source is public, and there are other OS components in the chain that
> > are not.
> >
> > Chrome is unable to launch with this malloc feature enabled, and crashes
> > during early startup, while loading the framework. From the user’s
> > perspective, when choosing to restart Chrome from the OS crash dialog,
> > this results in a secondary (and subsequent) crash.
> >
> > It’s possible to forcibly disable this malloc feature by environment
> > variable. The environment variable can be set in the app’s Info.plist.
> > While environment variables are only set from Info.plist when launched
> > via Launch Services (and not, for example, from a shell), the launch
> > from the macOS crash dialog does go through Launch Services, so this
> > should be a complete fix.
> >
> > Bug: 414750473
> > Change-Id: I0a9aba7d1ea0b94327252a706ddba686799d4863
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6501000
> > Reviewed-by: Avi Drissman <avi@chromium.org>
> > Commit-Queue: Mark Mentovai <mark@chromium.org>
> > Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> > Reviewed-by: Leonard Grey <lgrey@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1454086}
>
> Bug: 414750473
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Change-Id: I99f9434df068e8741ff15ca5b5ce6759b4df1e18
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6502113
> Auto-Submit: Nidhi Jaju <nidhijaju@chromium.org>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Owners-Override: Nidhi Jaju <nidhijaju@chromium.org>
> Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Cr-Commit-Position: refs/heads/main@{#1454260}

Bug: 414750473
Cq-Include-Trybots: luci.chromium.try:mac-official,mac11-arm64-rel,mac12-arm64-rel,mac13-arm64-rel,mac12-tests,mac13-tests,mac14-arm64-rel,mac14-tests,mac_chromium_dbg_ng,mac_chromium_11.0_rel_ng;luci.chrome.try:mac-chrome,mac-rel-ready
Change-Id: I4e7f72983b49046415999642bcd9382c5df0daaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6505920
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1455101}