feat(flag): replace '--slow' with '--parallel' (#5572)

Signed-off-by: knqyf263 <knqyf263@gmail.com>

pkg/semaphore/semaphore.go

@@ -4,27 +4,9 @@ import "golang.org/x/sync/semaphore"
 
 const defaultSize = 5
 
-type options struct {
-	size int64
-}
-
-type option func(*options)
-
-func WithDefault(n int64) option {
-	return func(opts *options) {
-		opts.size = defaultSize
+func New(parallel int) *semaphore.Weighted {
+	if parallel == 0 {
+		parallel = defaultSize
 	}
-}
-
-func New(slow bool, opts ...option) *semaphore.Weighted {
-	o := &options{size: defaultSize}
-	for _, opt := range opts {
-		opt(o)
-	}
-	if slow {
-		// Process in series
-		return semaphore.NewWeighted(1)
-	}
-	// Process in parallel
-	return semaphore.NewWeighted(o.size)
+	return semaphore.NewWeighted(int64(parallel))
 }