Move remote-diff-check related utilities to a shared location

[dario-piotrowicz]

In #10314, the following todo comments have been added for moving downloadWorkerConfig and Diff to a shared location:

workers-sdk/packages/wrangler/src/init.ts

Lines 229 to 230 in c4c8ff6

	// TODO: move this to a shared location
	export async function downloadWorkerConfig(

workers-sdk/packages/wrangler/src/cloudchamber/helpers/diff.ts

Lines 53 to 54 in c4c8ff6

	// TODO: move this Diff Class to a shared location (since it is not Cloudchamber specific)
	export class Diff {

This issue is for making sure we don't forget to do this.