6181 workflows create a custom code executor (#6235)

Closes #6181

## Testing
- download Altair graphql dev tool https://altairgraphql.dev/#download
- create a file locally `test.ts` containing:
```
export const handler = async (event: object, context: object) => {
  return { test: 'toto', data: event['data'] };
}
```
- play those requests in Altair:
mutation UpsertFunction($file: Upload!) {
  upsertFunction(name: "toto", file: $file)
}

mutation ExecFunction {
  executeFunction(name:"toto", payload: {data: "titi"})
}
- it will run the local driver, add those env variable to test with
lambda driver
```
CUSTOM_CODE_ENGINE_DRIVER_TYPE=lambda
LAMBDA_REGION=eu-west-2
LAMBDA_ROLE=<ASK_ME>
```

packages/twenty-server/src/engine/integrations/file-storage/utils/read-file-content.ts

@@ -0,0 +1,11 @@
+import { Readable } from 'stream';
+
+export const readFileContent = async (stream: Readable): Promise<string> => {
+  const chunks: Buffer[] = [];
+
+  for await (const chunk of stream) {
+    chunks.push(Buffer.from(chunk));
+  }
+
+  return Buffer.concat(chunks).toString('utf8');
+};