chore(stovepipe): rearrange stovepipe files into gateway subdirectory

[mnoah1]

We had initially set up a single stovepipe service, but we will actually use a similar model to submitqueue and have a gateway + orchestrator that can be deployed separately. This change shifts existing stovepipe files into the gateway and updates code references throughout.

After, I will add a stovepipe orchestrator and we can proceed to gradually rearrange the existing submitqueue files into this layout.

Why?

We're planning on the intended layout below, to better manage submitqueue + stovepipe as separate projects that have some shared dependencies but distinct deployability. This is an initial step toward getting to the layout below:

submitqueue/  
├── core/ 
│   ├── extension/   # common extensions go here
├── doc/
├── entity/          # common entities
├── example/      
├── submitqueue/
│   ├── gateway/
│   ├── orchestrator/
│   └── extension/  # sq-specific extensions
│   └── entity/     # sq-specific entities
├── stovepipe/
│   ├── gateway/  
│   ├── orchestrator/   
│   └── extension/  # stovepipe-specific extensions
│   └── entity/     # stovepipe-specific entities
├── test/
└── tool/

What?

Move files into gateway and move into directories

Test Plan

• make local-stovepipe-gateway-start
• CI

Issue