Improved exception handling

[dirkwhoffmann]

I'm currently working on an experimental WASM port that not only gives me the opportunity to learn something new (web stuff), but also exposes some areas of improvement regarding vAmiga’s API.

Binding the C++ core to JavaScript via Embind is fairly straightforward. However, it is notoriously difficult to pass exceptions from the C++ world into the JS world. I.e., it is fairly easy to signal that an exception has occurred, but it is cumbersome to get a grip on the contents of the triggered object.

Exception handling could be simplified by the following improvement:

• On the C++ side, all exceptions (except the internal ones used inside Moira) are thrown via a new function Amiga::throwException(), which stores a local copy of the thrown object before throwing it.
• On the JS side, if an exception is detected, the thrown object is reconstructed via the local copy stored inside vAmiga. Some new API methods have to be added to query the locally stored exception object.

[dirkwhoffmann]

Wontfix. It's easier to implement the functionality in the proxy layer of the WASM port.

Current state of the WASM port can be viewed here: https://vamigaonline.github.io

[dirkwhoffmann]

To avoid name clashes with Chris' web port, I've renamed mine to vAmiga.net: https://vamiganet.github.io