azureblob,b2,s3: fix chunksize calculations producing too many parts

Before this fix, the chunksize calculator was using the previous size
of the object, not the new size of the object to calculate the chunk
sizes.

This meant that uploading a replacement object which needed a new
chunk size would fail, using too many parts.

This fix fixes the calculator to take the size explicitly.

backend/s3/s3.go

@@ -2116,7 +2116,7 @@ type Options struct {
 	UploadCutoff          fs.SizeSuffix        `config:"upload_cutoff"`
 	CopyCutoff            fs.SizeSuffix        `config:"copy_cutoff"`
 	ChunkSize             fs.SizeSuffix        `config:"chunk_size"`
-	MaxUploadParts        int64                `config:"max_upload_parts"`
+	MaxUploadParts        int                  `config:"max_upload_parts"`
 	DisableChecksum       bool                 `config:"disable_checksum"`
 	SharedCredentialsFile string               `config:"shared_credentials_file"`
 	Profile               string               `config:"profile"`
@@ -4718,10 +4718,10 @@ func (o *Object) uploadMultipart(ctx context.Context, req *s3.PutObjectInput, si
 	if size == -1 {
 		warnStreamUpload.Do(func() {
 			fs.Logf(f, "Streaming uploads using chunk size %v will have maximum file size of %v",
-				f.opt.ChunkSize, fs.SizeSuffix(int64(partSize)*uploadParts))
+				f.opt.ChunkSize, fs.SizeSuffix(int64(partSize)*int64(uploadParts)))
 		})
 	} else {
-		partSize = chunksize.Calculator(o, int(uploadParts), f.opt.ChunkSize)
+		partSize = chunksize.Calculator(o, size, uploadParts, f.opt.ChunkSize)
 	}
 
 	memPool := f.getMemoryPool(int64(partSize))