feat(core): Introduce object store service (#7225)

Depends on https://github.com/n8n-io/n8n/pull/7220 | Story:
[PAY-840](https://linear.app/n8n/issue/PAY-840/introduce-object-store-service-and-manager-for-binary-data)

This PR introduces an object store service for Enterprise edition. Note
that the service is tested but currently unused - it will be integrated
soon as a binary data manager, and later for execution data.
`amazonaws.com` in the host is temporarily hardcoded until we integrate
the service and test against AWS, Cloudflare and Backblaze, in the next
PR.

This is ready for review - the PR it depends on is approved and waiting
for CI.

---------

Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/core/src/BinaryData/utils.ts

@@ -1,5 +1,7 @@
-import fs from 'fs/promises';
+import fs from 'node:fs/promises';
+import type { Readable } from 'node:stream';
 import type { BinaryData } from './types';
+import concatStream from 'concat-stream';
 
 /**
  * Modes for storing binary data:
@@ -20,3 +22,10 @@ export async function ensureDirExists(dir: string) {
 		await fs.mkdir(dir, { recursive: true });
 	}
 }
+
+export async function toBuffer(body: Buffer | Readable) {
+	return new Promise<Buffer>((resolve) => {
+		if (Buffer.isBuffer(body)) resolve(body);
+		else body.pipe(concatStream(resolve));
+	});
+}