[dagit] Fix Backfills page locking up when displaying large backfills…

…, improve "target" column (#11693)

### Summary & Motivation

I created a backfill of 180,000 partition keys and found that Dagit is
unable to render the Overview > Backfills page. It seems this is due to
several things:

- The API is returning a `PartitionStatuses` object for each backfill
containing an object for each partition. It'd be great to move this to
the ranges format that @clairelin135 is putting together which will pass
straight through to the rendering!

- Apollo cache is trying to normalize all of these 160k objects into
some sort of fancy cache, which it "deep partial updates" with the new
data. We can disable this behavior for just `PartitionStatus` with an
entry in AppCache.tsx, but I have mixed feelings about making global
changes. Maybe we do it for now and remove it when we move this status
data to a smaller / faster range format. It reduces the "page lock time"
after data is received from 7s to about 2s on my machine.

- The Backfill page is using the `<PartitionStatus />` component in
"separated bars" mode, which actually tries to render 180k divs for the
180k partitions.

This PR addresses the last two - if there are more than 1k partition
keys in the backfill, we now just render a box that is the same shape of
the PartitionStatus component but contains just the counts:


![image](https://user-images.githubusercontent.com/1037212/213035809-0e2638a6-c31c-4418-8879-f68e3fb71d56.png)


I also observed a lot of funkiness in the Backfill Target column because
I have both asset and job backfills for both loaded and unloaded
repositories in my test set. I changed the code so that it omits
partition set names that are part of hidden asset jobs, and made it show
asset keys even when the partition set isn't part of a loaded repo.

### How I Tested These Changes

Page loads!

For the target backfill changes, I attached before and after screenshots
and I think my setup tests all five cases (assets / non-assets + jobs /
asset graph / asset partition set).


![image](https://user-images.githubusercontent.com/1037212/212241840-0421a01d-d151-4843-89cf-f32a5a2350ed.png)

Co-authored-by: bengotow <bgotow@elementl.com>

js_modules/dagit/packages/core/src/app/AppCache.tsx

@@ -7,6 +7,11 @@ export const createAppCache = () =>
   new InMemoryCache({
     addTypename: true,
     possibleTypes,
+    typePolicies: {
+      PartitionStatus: {
+        keyFields: false,
+      },
+    },
     dataIdFromObject: (object: any) => {
       if (
         object.name &&
@@ -17,6 +22,8 @@ export const createAppCache = () =>
         return 'Instance';
       } else if (object.__typename === 'Workspace') {
         return 'Workspace';
+      } else if (object.__typename === 'PartitionBackfill') {
+        return object.backfillId;
       } else {
         return defaultDataIdFromObject(object);
       }