[Debugger] Add logpoints to the icon margin

[iainx]

A log point is a breakpoint that just prints a message and continues. Add
support for them to the icon margin.

Requires mono/debugger-libs#182

[mhutch]

How are these different from tracepoints?

[mhutch]

Some context:
microsoft/vscode#45128
microsoft/vscode-node-debug2#163

It looks like VS Code is calling tracepoints "logpoints". However, since VS also calls them tracepoints, I think we should stick with the existing name for now.

I can see value in having a "new tracepoint" command (like VS) that opens up the breakpoint editor already configured as a tracepoint. But I'm not sure about "toggle tracepoint" - we can't simply toggle a tracepoint on, we need to ask for an expression, which means showing a UI, and toggle off is already covered by the breakpoint toggle command.

Note also that in VS the breakpoint menu is shown in the editor, not the margin - because breakpoints can have a column offset too when there are multiple statements on one line.

I wonder whether we should investigate making it easier to change breakpoint properties after creation with something like the floating toolbar and inline access breakpoint properties like VS: https://blogs.msdn.microsoft.com/devops/2014/10/06/new-breakpoint-configuration-experience-in-visual-studio-2015.

[Therzok]

See #4518

[mhutch]

Yup. Definitely agree making this functionality more discoverable and usable is good, just think it needs some design work.

[Therzok]

Unit tests please

[slluis]

I agree with @mhutch. I don't think we need to introduce a new logpoint concept, and it makes more sense to have an Add command rather than toggle.

[jstedfast]

Based on the comments, it sounds like this should be closed? Or?

[iainx]

Yeah, it was a quick proof of concept, so closed