Add `Scoped` `Plugin` (#2759)

## Motivation and Context

The
[`FilterByOperationName`](https://docs.rs/aws-smithy-http-server/0.55.4/aws_smithy_http_server/plugin/struct.FilterByOperationName.html

)
allows the customer to filter application of a plugin. However this is a
_runtime_ filter. A faster and type safe alternative would be a nice
option.

## Description

Add `Scoped` `Plugin` and `scope` macro.

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Co-authored-by: david-perez <d@vidp.dev>