[ios] Sets refactoredNTP height in viewWillAppear

- Sets the contentSuggestion views constraints in viewWillAppear
instead of viewDidLoad. This helps with the initial layout where
everything was compressed, but still once the view is visible the
constraints are set in place.
- Calls updateContentSuggestionForCurrentLayout on
viewSafeAreaInsetsDidChange which fixes the compressed omnibox bug.
- Moves a bunch of layout calls from viewDidLayoutSubviews to
viewWillLayoutSubviews. This seems to have the same effect but it should
be smoother all around since there's not an abrupt change after the
layout.
- Removes unnecessary code related to fake omnibox layouting.

Bug: 1114792
Change-Id: I1da38c7e961c47febde503ed1cdb9cb76b07205b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2714003
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Adam Trudeau-Arcaro <adamta@google.com>
Cr-Commit-Position: refs/heads/master@{#856773}