gopls: add a command to jump to the gopls debug server

[findleyr]

In golang/go#45518, we added a command to gopls to start the debug server if it wasn't running, and return its address. This has the potential to make troubleshooting significantly easier.

We should expose an easy way for users to navigate to the debug server from vscode-go. Naively, we could add a menu item that would run this command and jump to the URL that was returned.

CC @hyangah @stamblerre

[hyangah]

@stamblerre @findleyr I think we can start with a command that wraps invoking the gopls command + opening the returned address (in the external browser). Is the exposure of this feature through the menu item, rather than through Command Palette important?

[findleyr]

Is the exposure of this feature through the menu item, rather than through Command Palette important?

Definitely not. A command is probably all that is needed.