Fix for count being very slow on large Parse Classes' collections (Postgres) (#5330)

* Changed count to be approximate. Should help with postgres slowness

* refactored last commit to only fall back to estimate if no complex query

* handlign variables correctly

* Trying again because it was casting to lowercase table names which doesnt work for us/

* syntax error

* Adding quotations to pg query

* hopefully final pg fix

* Postgres will now use an approximate count unless there is a more complex query specified

* handling edge case

* Fix for count being very slow on large Parse Classes' collections in Postgres. Replicating fix for Mongo in issue 5264

* Fixed silly spelling error resulting from copying over notes

* Lint fixes

* limiting results to 1 on approximation

* suppress test that we can no longer run for postgres

* removed tests from Postgres that no longer apply

* made changes requested by dplewis

* fixed count errors

* updated package.json

* removed test exclude for pg

* removed object types from method

* test disabled for postgres

* returned type

* add estimate count test

* fix mongo test

src/Controllers/DatabaseController.js

@@ -1324,7 +1324,9 @@ class DatabaseController {
       })
       .then((schema: any) => {
         return this.collectionExists(className)
-          .then(() => this.adapter.count(className, { fields: {} }))
+          .then(() =>
+            this.adapter.count(className, { fields: {} }, null, '', false)
+          )
           .then(count => {
             if (count > 0) {
               throw new Parse.Error(