Use zero-copy approach to convert types between string and byte… (#2206)

* Use zero-copy approach to convert types between string and byte slice

* Rename argument to a eligible one

Benchmark:

BenchmarkBytesConvBytesToStrRaw-4   	21003800	        70.9 ns/op	      96 B/op	       1 allocs/op
BenchmarkBytesConvBytesToStr-4      	1000000000	         0.333 ns/op	       0 B/op	       0 allocs/op
BenchmarkBytesConvStrToBytesRaw-4   	18478059	        59.3 ns/op	      96 B/op	       1 allocs/op
BenchmarkBytesConvStrToBytes-4      	1000000000	         0.373 ns/op	       0 B/op	       0 allocs/op


Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

gin.go

@@ -13,6 +13,7 @@ import (
 	"path"
 	"sync"
 
+	"github.com/gin-gonic/gin/internal/bytesconv"
 	"github.com/gin-gonic/gin/render"
 )
 
@@ -477,7 +478,7 @@ func redirectFixedPath(c *Context, root *node, trailingSlash bool) bool {
 	rPath := req.URL.Path
 
 	if fixedPath, ok := root.findCaseInsensitivePath(cleanPath(rPath), trailingSlash); ok {
-		req.URL.Path = string(fixedPath)
+		req.URL.Path = bytesconv.BytesToString(fixedPath)
 		redirectRequest(c)
 		return true
 	}