Delete `aws_smithy_http::ResolveEndpoint` and point usages to service-specific trait (#3078)

## Motivation and Context
- Fixes https://github.com/awslabs/smithy-rs/issues/3043

As a follow up to #3072 this removes the old endpoint resolver
interfaces in favor of creating a per-service resolver trait.

This trait defines a `into_shared_resolver()` method which converts the
local trait into a global resolver that can be used with the
orchestrator.

## Description
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## Testing
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## Checklist
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rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

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