Do not normalize input resolution for scale_resolution_down_to in simulcast.

When scale_resolution_down_by is unset, NormalizeResolution rounds the
input resolution down to a multiple of 2^(max_num_layers - 1) assuming
default 1/2 simulcast scaling. Passing that normalized resolution into
GetLayerResolutionFromScaleResolutionDownTo truncates stream dimensions
even when scale_resolution_down_to is used, causing VideoStreamEncoder
to crop incoming frames.

Pass the original unnormalized frame dimensions to
GetLayerResolutionFromScaleResolutionDownTo, matching
CreateDefaultVideoStreams.

Bug: b/567616289
Change-Id: Ie73a346ba4f09e9a4e58d9a60de58019c2ab8974
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/507760
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48814}