Make service config builder contain `CloneableLayer` (#2795)

## Motivation and Context
This PR will reduce fields in service config builders to contain only
`CloneableLayer` (except for `interceptors` and `identity_resolvers`).

## Description
This is the third PR in a series of config refactoring in the
orchestrator mode. Just like #2762, this PR reduces fields in service
config builders to contain `CloneableLayer`.

The code changes follow a straightforward pattern where builders'
setters are implemented via a config layer.

## Testing
Relies on the existing tests in CI

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Co-authored-by: Yuki Saito <awsaito@amazon.com>
Co-authored-by: Zelda Hessler <zhessler@amazon.com>