refactor: move boomer from hrp internal to pkg

hrp/pkg/boomer/task.go

@@ -0,0 +1,13 @@
+package boomer
+
+// Task is like the "Locust object" in locust, the python version.
+// When boomer receives a start message from master, it will spawn several goroutines to run Task.Fn.
+// But users can keep some information in the python version, they can't do the same things in boomer.
+// Because Task.Fn is a pure function.
+type Task struct {
+	// The weight is used to distribute goroutines over multiple tasks.
+	Weight int
+	// Fn is called by the goroutines allocated to this task, in a loop.
+	Fn   func()
+	Name string
+}