Rename test data files to be consistently lowercase. (#506)

Co-authored-by: Maggie Nolan <nolanmar@google.com>

internal/driver/driver_test.go

 		{"weblist=line[13],addresses,flat", "cpu"},
 		{"tags,tagfocus=400kb:", "heap_request"},
 		{"tags,tagfocus=+400kb:", "heap_request"},
-		{"dot", "longNameFuncs"},
-		{"text", "longNameFuncs"},
+		{"dot", "long_name_funcs"},
+		{"text", "long_name_funcs"},
 	}
 
 	baseVars := pprofVariables
 		p = contentionProfile()
 	case "symbolz":
 		p = symzProfile()
-	case "longNameFuncs":
+	case "long_name_funcs":
 		p = longNameFuncsProfile()
 	default:
 		return nil, "", fmt.Errorf("unexpected source: %s", s)
 	}
 }
 
-// longNameFuncsProfile returns a profile with function names which should be shortened in
-// graph and flame views.
+// longNameFuncsProfile returns a profile with function names which should be
+// shortened in graph and flame views.
 func longNameFuncsProfile() *profile.Profile {
 	var longNameFuncsM = []*profile.Mapping{
 		{