Ignore bookmark icon url when browser gets bookmark form sync cloud

[AlexeyBarabash]

Intended t o fix brave/brave-browser#7893

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Test Plan:

See steps in brave/brave-browser#7893

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[AlexeyBarabash]

Some details.
Seeing

[9788:9788:0124/132232.884549:ERROR:bookmark_specifics_conversions.cc(295)] Invalid bookmark: specifics cannot have an icon_url without having a favicon.

which get us into https://source.chromium.org/chromium/chromium/src/+/79.0.3945.130:components/sync_bookmarks/bookmark_specifics_conversions.cc;l=295

[AlexeyBarabash]

Chromium sends both icon_url and icon_data in the same time and expects to have them either both or either none of them.

Here is a place where Chromium creates BookmarkSpecifics with icon data.

sync_pb::EntitySpecifics CreateSpecificsFromBookmarkNode(
    const bookmarks::BookmarkNode* node,
    bookmarks::BookmarkModel* model,
    bool force_favicon_load)

https://source.chromium.org/chromium/chromium/src/+/79.0.3945.130:components/sync_bookmarks/bookmark_specifics_conversions.cc;bpv=1;bpt=1;l=134

force_favicon_load is set to false only in tests.

It was a time when we put bookmark icon data into SyncRecord metadata to allow to get the boookmark instantly.
We reverted that at the that time because:

1. S3 sync records for bookmarks with icons became too big as for a simple sync record;
2. There were a cases when client tried to sending update record and that mixed with newly came sync record making mess;
3. Mobile clients in anyway does not send icon bitmap, as it is not in our spec.

I marking this PR as ready for review to allow issue be fixed asap. For the matter of icon, I creating a new issue just found brave/brave-browser#4095 (comment), we are good to load icon once the page will be visited.

[bsclifton]

Merging as this is required to unblock some items for 1.3. CI has passed and PR has been peer reviewed 😄👍