[#1310] object: Move target initialization to separate package

* Split the logic of write target initialization to different packages;
* Refactor patch and put services: since both service initialize the target
  themselves.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

pkg/services/object/common/target/builder.go

@@ -0,0 +1,54 @@
+package target
+
+import (
+	"context"
+
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/transformer"
+)
+
+var _ transformer.ChunkedObjectWriter = (*inMemoryObjectBuilder)(nil)
+
+type inMemoryObjectBuilder struct {
+	objectWriter transformer.ObjectWriter
+	payload      *payload
+
+	obj *objectSDK.Object
+}
+
+func newInMemoryObjectBuilder(objectWriter transformer.ObjectWriter) *inMemoryObjectBuilder {
+	return &inMemoryObjectBuilder{
+		objectWriter: objectWriter,
+		payload:      getPayload(),
+	}
+}
+
+func (b *inMemoryObjectBuilder) Close(ctx context.Context) (*transformer.AccessIdentifiers, error) {
+	defer func() {
+		putPayload(b.payload)
+		b.payload = nil
+	}()
+
+	b.obj.SetPayload(b.payload.Data)
+
+	if err := b.objectWriter.WriteObject(ctx, b.obj); err != nil {
+		return nil, err
+	}
+
+	id, _ := b.obj.ID()
+	return &transformer.AccessIdentifiers{
+		SelfID: id,
+	}, nil
+}
+
+func (b *inMemoryObjectBuilder) Write(_ context.Context, p []byte) (int, error) {
+	b.payload.Data = append(b.payload.Data, p...)
+
+	return len(p), nil
+}
+
+func (b *inMemoryObjectBuilder) WriteHeader(_ context.Context, obj *objectSDK.Object) error {
+	b.obj = obj
+
+	return nil
+}