(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

test/server/lib/DocApi.ts

@@ -1029,6 +1029,24 @@ function testDocApi() {
         {id: [1, 2, 3, 4], A: [1, 33, 66, "$33"], B: [2, 1, 6, 0]},
       );
 
+      // Test bulk case with a mixture of record shapes
+      await check([
+          {
+            require: {A: 1},
+            fields: {A: 111},
+          },
+          {
+            require: {A: 33},
+            fields: {A: 222, B: 444},
+          },
+          {
+            require: {id: 3},
+            fields: {A: 555, B: 666},
+          },
+        ],
+        {id: [1, 2, 3, 4], A: [111, 222, 555, "$33"], B: [2, 444, 666, 0]},
+      );
+
       // allow_empty_require option with empty `require` updates all records
       await check([
           {