(core) Add BulkAddOrUpdateRecord action for efficiency

Summary:
This diff adds a new `BulkAddOrUpdateRecord` user action which is what is sounds like:

- A bulk version of the existing `AddOrUpdateRecord` action.
- Much more efficient for operating on many records than applying many individual actions.
- Column values are specified as maps from `colId` to arrays of values as usual.
- Produces bulk versions of `AddRecord` and `UpdateRecord` actions instead of many individual actions.

Examples of users wanting to use something like `AddOrUpdateRecord` with large numbers of records:

- https://grist.slack.com/archives/C0234CPPXPA/p1651789710290879
- https://grist.slack.com/archives/C0234CPPXPA/p1660743493480119
- https://grist.slack.com/archives/C0234CPPXPA/p1660333148491559
- https://grist.slack.com/archives/C0234CPPXPA/p1663069291726159

I tested what made many `AddOrUpdateRecord` actions slow in the first place. It was almost entirely due to producing many individual `AddRecord` user actions. About half of that time was for processing the resulting `AddRecord` doc actions. Lookups and updates were not a problem. With these changes, the slowness is gone.

The Python user action implementation is more complex but there are no surprises. The JS API now groups `records` based on the keys of `require` and `fields` so that `BulkAddOrUpdateRecord` can be applied to each group.

Test Plan: Update and extend Python and DocApi tests.

Reviewers: jarek, paulfitz

Reviewed By: jarek, paulfitz

Subscribers: jarek

Differential Revision: https://phab.getgrist.com/D3642

app/plugin/TableOperationsImpl.ts

@@ -5,6 +5,7 @@ import { arrayRepeat } from './gutil';
 import flatMap = require('lodash/flatMap');
 import isEqual = require('lodash/isEqual');
 import pick = require('lodash/pick');
+import groupBy = require('lodash/groupBy');
 
 /**
  * An implementation of the TableOperations interface, given a platform
@@ -59,8 +60,21 @@ export class TableOperationsImpl implements TableOperations {
         allow_empty_require: upsertOptions?.allowEmptyRequire
       };
       const recordOptions: OpOptions = pick(upsertOptions, 'parseStrings');
-      const actions = records.map(rec =>
-        ["AddOrUpdateRecord", tableId, rec.require, rec.fields || {}, options]);
+
+      // Group records based on having the same keys in `require` and `fields`.
+      // A single bulk action will be applied to each group.
+      // We don't want one bulk action for all records that might have different shapes,
+      // because that would require filling arrays with null values.
+      const recGroups = groupBy(records, rec => {
+        const requireKeys = Object.keys(rec.require).sort().join(',');
+        const fieldsKeys = Object.keys(rec.fields || {}).sort().join(',');
+        return `${requireKeys}:${fieldsKeys}`;
+      });
+      const actions = Object.values(recGroups).map(group => {
+        const require = convertToBulkColValues(group.map(r => ({fields: r.require})));
+        const fields = convertToBulkColValues(group.map(r => ({fields: r.fields || {}})));
+        return ["BulkAddOrUpdateRecord", tableId, require, fields, options];
+      });
       await this._applyUserActions(tableId, [...fieldNames(records)],
                                    actions, recordOptions);
       return [];