Add the ability to disable interceptors via the config bag (#2757)

This replaces the existing custom interceptor disable logic with shared
logic to allow generally disabling any public interceptors from Runtime
plugins. The previous behavior was very brittle because it relied
heavily on runtime plugin execution order.

## Motivation and Context
- simplify presigning behavior
- generalize logic to disable interceptors

## Description
Create `disable_interceptor` struct, which, when inserted into the
configuration bag can disable an interceptor via the `Interceptors`
execution interface.

## Testing
- ` (cd aws/sdk/build/aws-sdk/sdk/s3 && cargo test --test presigning)`

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._