refactor(core): move single-service core packages under the service that uses them

[roychying]

Why?

submitqueue/core/ is infra shared between the domain's services, so it should not depend on one. After the split, files there that resolve stores name a service's aggregate (the inversion raised in #740 and #741 ).

What?

Moves the packages that serve exactly one service:

From	To
core/batch/*	orchestrator/core/batch
core/request/{log,terminate}.go	orchestrator/core/request
core/request/{materializer,request}.go	gateway/core/request

core/request divides along the publish/persist line: the orchestrator publishes lifecycle events on the log topic, the gateway persists them.

core/changeset could not move for now — seven domain-level extension packages still depend on it. Relocating it would have created a new inversion. Instead it declares the slice of an aggregate it
needs:

type Stores interface {
    GetRequestStore() storage.RequestStore
    GetChangeStore()  storage.ChangeStore
}
type Resolve func(queue string) (Stores, error)

No file under submitqueue/core/ imports a service package now.

Test Plan

• go build ./..., go vet ./..., and all four repo checks clean;
• make test 122/122.

Issue