proc,service,terminal: add events call use it for dld notifications (#3980)

Add a GetEvents method that can be used to retrieve debug events, adds
events for downloading debug info through debuginfod and shows those
events in the command line client as well as console messages in DAP.

In the future this events mechanism can be used to unify EBPF
tracepoints with old style tracepoints.

Update #3906

service/api/types.go

@@ -411,6 +411,10 @@ type DebuggerCommand struct {
 	// Expr is the expression argument for a Call command
 	Expr string `json:"expr,omitempty"`
 
+	// If WithEvents is set events are generated that should be read by calling
+	// GetEvents.
+	WithEvents bool
+
 	// UnsafeCall disables parameter escape checking for function calls.
 	// Go objects can be allocated on the stack or on the heap. Heap objects
 	// can be used by any goroutine; stack objects can only be used by the
@@ -684,3 +688,22 @@ type GuessSubstitutePathIn struct {
 	ClientGOROOT            string
 	ClientModuleDirectories map[string]string
 }
+
+// Event is an event that happened during execution of the debugged program.
+type Event struct {
+	Kind EventKind
+	*BinaryInfoDownloadEventDetails
+}
+
+type EventKind uint8
+
+const (
+	EventResumed EventKind = iota
+	EventStopped
+	EventBinaryInfoDownload
+)
+
+// BinaryInfoDownloadEventDetails describes the details of a BinaryInfoDownloadEvent
+type BinaryInfoDownloadEventDetails struct {
+	ImagePath, Progress string
+}