debug: support data breakpoints (watchpoint)

[ripplewang888]

Is your feature request related to a problem? Please describe.
As gdb does, break at a watch point for when a variable value change. Delve support watch command, but I cant' execute this command
in vscode.

Describe the solution you'd like
(dlv) watch -rw b
Watchpoint b set at 0x556188
(dlv) l

how to do this in vscode? I want to set a watchpoint break.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[ripplewang888]

I think should add two menu bars when right click global variables.

[ripplewang888]

@gopherbot can you assign this issue to sb?

[hyangah]

I guess the closest is data breakpoint. Delve DAP (the debug adapter behind the scene) is not supporting data breakpoints yet.

https://github.com/go-delve/delve/blob/a164b89df10aba455e0196222e51fa4b65e5746c/service/dap/server.go#L796-L799

Contribution to DAP (in the go-delve repo) is welcome.

[ripplewang888]

@hyangah , thanks.
Do you know when to support this feature?