Use configurable limit for page print requests.

This is in the same context of increasing the limit of page size we
could send to the backend. Hence we renamed the flag as well.

Things to focus in the review: 1) Is this upload synchronous and
blocking user? In that case we might need more logic to do the upload
async. 2) I am using the same finch flag here, let me know if you prefer
a separate one.

Change-Id: Ib24a26bbf1a3b2b845169994a1122a92bf7ca0e6
Bug: 417992384
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6622118
Reviewed-by: Dominique Fauteux-Chapleau <domfc@chromium.org>
Commit-Queue: Elias Homsi <eliashomsi@google.com>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Nancy Xiao <nancylanxiao@google.com>
Auto-Submit: Elias Homsi <eliashomsi@google.com>
Cr-Commit-Position: refs/heads/main@{#1470003}