Add type inference to `loadBeforeMutationEntities` and `loadAfterMutationEntities`

[genu]

Is there a reliable way to infer the proper return type of loadAfterMutationEntities and loadBeforeMutationEntities?

zenstack-v3/packages/runtime/src/client/plugin.ts

Lines 170 to 174 in 35a9e0d

	/**
	* Loads the entities that have been mutated.
	*/
	loadAfterMutationEntities(): Promise<Record<string, unknown>[] | undefined>;

zenstack-v3/packages/runtime/src/client/plugin.ts

Lines 153 to 158 in 35a9e0d

	/**
	* Loads the entities that are about to be mutated. The db operation that loads the entities is executed
	* within the same transaction context as the mutation.
	*/
	loadBeforeMutationEntities(): Promise<Record<string, unknown>[] | undefined>;

If the return data is typed, it becomes easier working with any follow up queries:

export const onAfterPostDelete = definePlugin<SchemaType>({
  id: "onAfterPostDelete",
  onEntityMutation: {
    async beforeEntityMutation({ model, action, loadBeforeMutationEntities, client, queryId }) {
      const deletedPost = await loadBeforeMutationEntities() // <--- typed as Record<string, unknown>[] | undefined but its really a Post[]

      if (action === "delete" && model === "Post") {
        // Do some logic
        const tags = await client.tag.findMany({
          where: {
            postId: deletedPost[0].id, // <-- This doesn't work unless we cast deletedPost to proper type like Post[]
          },
        })
      }
    },
  },
})