Show only user goroutines by default

[suzmue]

Using a debugger to debug a Go program reveals a lot of the Go runtime implementation details to the user. Several goroutines that belong to the runtime appear in the call stack, cluttering the view and making a simple program seem very complicated.

For example when debugging a simple hello world program, 5 different goroutines appear in the callstack:
Program stopped on a breakpoint in main.go:

Call stack:

This proposal is to (by default) only show the user goroutines in the call stack. When using this new default, the call stack for hello world will only show a single goroutine, as would be expected from a simple program with no concurrency:

This would be controlled by a setting to allow users that really want to see the system goroutines to include them using the launch configuration.

[hyangah]

I don't see any issue or objection, but positive votes. Let's move to the issue tracker and make it work.

Created #1797