[PIX] Disable feature in landscape mode

Since the payments platform doesn't support Pix payment in the landscape
mode yet, the Pix flow should be disabled in the landscape mode on the
client side.

Whenever the payments platform is ready, the feature can be rolled out
on the client side using EnablePixPaymentsInLandscapeMode flag.

Bug: 365643174, b/365644074
Change-Id: I401b69ad242fea6c87a45881b13bf8c7676689b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5849378
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Vishwas Uppoor <vishwasuppoor@google.com>
Cr-Commit-Position: refs/heads/main@{#1353474}