feat(core): flatten provider config and load native packages (#35563)

Co-authored-by: Dax Raad <d@ironbay.co>

packages/llm/src/provider-package.ts

@@ -0,0 +1,16 @@
+import type { Model } from "./schema"
+
+export interface Settings extends Readonly<Record<string, unknown>> {
+  readonly headers?: Readonly<Record<string, string>>
+  readonly body?: Readonly<Record<string, unknown>>
+  readonly limits?: {
+    readonly context: number
+    readonly output: number
+  }
+}
+
+export interface Definition<ProviderSettings extends Settings = Settings> {
+  readonly model: (modelID: string, settings: ProviderSettings) => Model
+}
+
+export * as ProviderPackage from "./provider-package"