(core) Remove transform columns on shutdown

Summary: Call a new user action `RemoveTransformColumns` in ActiveDoc shutdown.

Test Plan: Added nbrowser test

Reviewers: georgegevoian, paulfitz

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D4107

test/nbrowser/RemoveTransformColumns.ts

@@ -0,0 +1,35 @@
+import {assert, driver} from 'mocha-webdriver';
+
+import * as gu from 'test/nbrowser/gristUtils';
+import {server, setupTestSuite} from "test/nbrowser/testUtils";
+
+describe('RemoveTransformColumns', function () {
+  this.timeout(4000);
+  setupTestSuite();
+
+  it('should remove transform columns when the doc shuts down', async function () {
+    await server.simulateLogin("Chimpy", "chimpy@getgrist.com", 'nasa');
+    const doc = await gu.importFixturesDoc('chimpy', 'nasa', 'Horizon', 'RemoveTransformColumns.grist', false);
+    await driver.get(`${server.getHost()}/o/nasa/doc/${doc.id}`);
+    await gu.waitForDocToLoad();
+
+    assert.deepEqual(await gu.getVisibleGridCells({col: 'B', rowNums: [1]}), [
+      'manualSort, A, B, C, ' +
+      'gristHelper_Converted, gristHelper_Transform, ' +
+      'gristHelper_Converted2, gristHelper_Transform2'
+    ]);
+
+    const userAPI = gu.createHomeApi('chimpy', 'nasa');
+    await userAPI.applyUserActions(doc.id, [["Calculate"]]);  // finish loading fully
+    await userAPI.getDocAPI(doc.id).forceReload();
+    await driver.get(`${server.getHost()}/o/nasa/doc/${doc.id}`);
+    await gu.waitForDocToLoad();
+
+    assert.deepEqual(await gu.getVisibleGridCells({col: 'B', rowNums: [1]}), [
+      'manualSort, A, B, C'
+    ]);
+
+    await gu.checkForErrors();
+  });
+
+});