Fixes #2487

Closes #2481

Instead of EF.Functions, as we normally do with Npgsql-specific types.

Part of #2470

Sync EF Core to 7.0.0-rc.1.22410.9

Part of #2450

Following https://github.com/dotnet/efcore/pull/28492

Part of #2450

Fixes #2454

Basically a copy-paste of:

* https://github.com/dotnet/efcore/pull/28477
* https://github.com/dotnet/efcore/pull/28529

Closes #2445

Fixes #2439

And use Npgsql 7.0.0-preview.6, dotnet SDK 7.0.0-preview.6

Closes #2433

Closes #2384

This reverts commit 39fa68de.

Closes #2339

* string_agg (string.Join)
* array_agg
* json_agg/jsonb_agg
* json_object_agg/jsonb_object_agg
* range_agg, range_intersect_agg
* Aggregate statistics functions

Closes #2395
Closes #532

Closes #2384

Instead of our PG-specific one.

Fixes #2406

Takes care of the built-in aggregates only for now (Min/Max/etc.)

Part of #727

Fixes #2389