feat: add Delete method to remove scopes

[ohroy]

fix #139

• Resolved an issue where Shutdown didn't essentially remove the container. Essentially, this is a memory leak. (For example, I create a request scooe every time I make a request, and when I make a lot of requests, the containers will become more and more.)
• To maintain API compatibility, here are two new APIs

Delete() *ShutdownReport 
Delete(ctx context.Context) *ShutdownReport

Essentially it's still calling Shutdown internally, and then appending the code from the parent scope. If itself is root scope, then do nothing.

• Also add a test to verify logic