The main motivator here was noticing that --disable-sql-database did not
work with AppKit. Rather than re-implementing this there, move ownership
of these classes to WebView::Application, so that each UI does not need
to individually worry about it.
The identifier "Protocol" is claimed by Objective-C and Swift for use
by the language's built-in protocol conformance feature, which is
similar to Rust traits or Java interfaces.
Rename LibProtocol -> LibRequests, and its namespace from Protocol to
Requests to accomodate this.
Currently, if we want to add a new e.g. WebContent command line option,
we have to add it to all of Qt, AppKit, and headless-browser. (Or worse,
we only add it to one of these, and we have feature disparity).
To prevent this, this moves command line flags to WebView::Application.
The flags are assigned to ChromeOptions and WebContentOptions structs.
Each chrome can still add its platform-specific options; for example,
the Qt chrome has a flag to enable Qt networking.
There should be no behavior change here, other than that AppKit will now
support command line flags that were previously only supported by Qt.
Previously, the browser would crash when opening a task manager window
with the `--enable-qt-networking` flag set because we were passing the
default WebContentOptions to the underlying WebContentView.
This is the same behavior as RequestServer, with the added benefit that
we know how to gracefully reconnect ImageDecoder to all WebContent
processes on restart.
