[iOS] Add handling long notes in add password view of CPE

Password notes have max length of 1000 across platforms. This CL:
* Adds displaying warning text in footer when note length crosses 900
chars
* Adds disabling save button, changing note text color to red and
displaying error icon when note length crosses 1000 chars

Screencast: https://drive.google.com/file/d/1-pNKK62J5zRFNBKGkfpNRQ1T0CHAL_Xz/view?usp=sharing

Bug: 1414897
Change-Id: Id8fe43d06357b7c95d94281311a24eb656ddc59a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4348501


Reviewed-by: Robbie Gibson <rkgibson@google.com>
Commit-Queue: Rafał Godlewski <rgod@google.com>
Cr-Commit-Position: refs/heads/main@{#1118910}