LibWeb: Calling Web::Page::load_html(StringView) in a loop causes memory leak

[ADKaster]

This comes into play when loading the TaskManager window's generated HTML. While the approach of using HTML and a WebView for a simple table view is dubious, the behavior of constantly increasing the GC Heap's maximum size threshold leads to unbounded memory usage as we hit the load_html IPC call once a second.

We should find a way to control this memory usage, or perhaps to give navigation information to the GC heuristics, to limit this RAM growth.