Support paging of stack frames

[weinand]

Currently we show only a fixed number (20) of frames of a stack trace.
We should improve this in the following way:

• in the CALLSTACK view show a 'more' affordance at the bottom of the stack trace if there are more frames available than the PAGESIZE specifies.
• pressing 'more' loads another PAGESIZE frames.
• if there are no frames available no 'more' affordance is shown.
• the PAGESIZE value can be configured in the debug settings.

[weinand]

@isidorn I've added paging support to the debug protocol, vscode and node-debug.

[weinand]

@isidorn backward compatibility: if StackTraceResponse has no totalFrames attribute, fall back to old semantics, that is do not show 'more' button.

[isidorn]

@weinand check it out and let me know what you think.
I will also create a test plan item for this. Here it is #4819

[weinand]

@stevencl I think we need your help with the UX for this:

I think we should at least use a different font face, e.g. Italic to make it clear the "Load more stack frames" is not a frame but an action.