Rust Tabs engine should trim tabs list before upload to keep payload under the max size

[mhammond]

Desktop tabs does a couple of things we should:

• Checks each URL is under the max size for a URL
• Checks that the total payload size is smaller than the max, and drops tabs until it is

The second in particular will stop any tabs for a device being listed, and is what I suspect is happening in this bug

We might as well do this in the rust component before we vendor it into m-c. cc @skhamis

┆Issue is synchronized with this Jira Task ┆epic: Tabs improvements