[PropertyView] MultiValues of type 'text' disappear on save

On some occasions, when a Property contains multiple values of type `text` that also contain multiple lines and the document is saved to a file and loaded again, the multi values except for the very first will be lost. The first value will also be truncated and only contain the first line of the original value.

Start at the PropertyView code and reproduce the save-and-reload case with multiple multiline text values. Trace how these values are serialized and loaded, then verify that every value retains all of its original lines after the document is reopened.

Written by the indexing model from the issue text.