[Extension type] Web debugging support

[itsjustkevin]

[eernstg]

Please note that this feature has been renamed: It is now the 'inline class' feature.

[annagrin]

We fixed a couple of issues where expression evaluation of extension types did not work:

• [ddc] extension type method calls for static interop in expression evaluation fail at runtime  #53048
• [incremental compiler] Cannot compile expression containing extension type #53036

So for the short term extension types "work" from the debugger perspective, but the users would not have much useful information about the extension types as they do not exist at runtime.

Providing a useful experience would require bigger changes though the whole tooling ecosystem:

• Design: describe how we present the static extension types to the user in the debugger UI
• CFE (incremental compiler), frontend server, expression compiler worker: provide static types to the expression evaluation API.
• vm service, vm, dwds: use the new API
• DevTools: present static types and using new vm service API

Opened an issue to track: #53461