fwdata text with runs (styles/ws spans) in it will be overwritten if changed

[hahn-kev]

Describe the bug
Some fields can contain complex text data, we want to make data that is complex read only on the client. This is not a field by field setting, but for each string of data from a project. In FwDataMiniLcm we have the method FromLcmMultiString which converts from Lcm to MiniLcm, we want to augment it like this to detect if the data should be readonly:

private MultiString FromLcmMultiString(ITsMultiString multiString)
{
    var result = new MultiString(multiString.StringCount);
    for (var i = 0; i < multiString.StringCount; i++)
    {
        var tsString = multiString.GetStringFromIndex(i, out var ws);
        if (tsString.RunCount == 1)
        {
            result.Values.Add(GetWritingSystemId(ws), tsString.Text);
        }
        else
        {
            //todo, mark this value as read only so we don't edit it and overwrite text
        }
    }

    return result;
}

note checking that RunCount is 1. I'm not sure how we want to mark a value as read only. One option would be to add another ws key "{wsId}-ro": "true", or we could modify the text itself, but that would be more complicated as it would require escaping. The frontend could then respect this configuration and make those text fields readonly. Later on once we model and support runs we can change this and the frontend won't be readonly anymore.