Support rendering numbers in variables list in hex

[DanTup]

Requested by @timsneath.. It would be useful to be able to view values in hex format in the variables view.

VS Code/DAP only work with strings so cannot provide formatting themselves, but the recommended way seems to be to contribute a context menu entry and handle it ourselves:

microsoft/vscode#28025 (comment)

This might need both work in the DAP and the VS Code extension (I'm also unsure whether this interacts with the ValueFormat in DAP spec, or if that's still VS-only).

[DanTup]

Also opened microsoft/vscode#148125, since there are comments suggesting there may be a plan to move to the DAP standard way (ValueFormat) which would be much better than having to have non-standard DAP work and extra commands in the VS Code extension. If it seems like that might happen soon, it might be worth waiting for - but otherwise a command/custom request in the meantime might be worthwhile.

[timsneath]

Super! Yeah, VS proper has support for this as a debugger-wide setting (see last sentence of this section), so I was a little surprised to hear that it would require custom work at the extension level. Thrilled to see it on the backlog!