(core) External requests

Summary:
Adds a Python function `REQUEST` which makes an HTTP GET request. Behind the scenes it:

- Raises a special exception to stop trying to evaluate the current cell and just keep the existing value.
- Notes the request arguments which will be returned by `apply_user_actions`.
- Makes the actual request in NodeJS, which sends back the raw response data in a new action `RespondToRequests` which reevaluates the cell(s) that made the request.
- Wraps the response data in a class which mimics the `Response` class of the `requests` library.

In certain cases, this asynchronous flow doesn't work and the sandbox will instead synchronously call an exported JS method:

- When reevaluating a single cell to get a formula error, the request is made synchronously.
- When a formula makes multiple requests, the earlier responses are retrieved synchronously from files which store responses as long as needed to complete evaluating formulas. See https://grist.slack.com/archives/CL1LQ8AT0/p1653399747810139

Test Plan: Added Python and nbrowser tests.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Subscribers: paulfitz, dsagal

Differential Revision: https://phab.getgrist.com/D3429

app/server/lib/GranularAccess.ts

@@ -4,7 +4,13 @@ import { ActionGroup } from 'app/common/ActionGroup';
 import { createEmptyActionSummary } from 'app/common/ActionSummary';
 import { ServerQuery } from 'app/common/ActiveDocAPI';
 import { ApiError } from 'app/common/ApiError';
-import { AddRecord, BulkAddRecord, BulkColValues, BulkRemoveRecord, BulkUpdateRecord } from 'app/common/DocActions';
+import {
+  AddRecord,
+  BulkAddRecord,
+  BulkColValues,
+  BulkRemoveRecord,
+  BulkUpdateRecord,
+} from 'app/common/DocActions';
 import { RemoveRecord, ReplaceTableData, UpdateRecord } from 'app/common/DocActions';
 import { CellValue, ColValues, DocAction, getTableId, isSchemaAction } from 'app/common/DocActions';
 import { TableDataAction, UserAction } from 'app/common/DocActions';