.Net: Ensure MongoDB filter/offset tests don't conflict (#12739)

### Motivation and Context

Two of the MongoDB tests intermittently fail when run on our CI (once
they are enabled).

This is, I believe, because two different tests are using and setting up
the same collection name.

### Description

Rename the Filter test to not use the Offset test collection name.

### Contribution Checklist

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Author: damieng

dotnet/src/IntegrationTests/Connectors/Memory/CosmosMongoDB/CosmosMongoCollectionTests.cs

@@ -390,7 +390,7 @@ public async Task SearchReturnsValidResultsWithFilterAsync()
         var hotel3 = this.CreateTestHotel(hotelId: "key3", embedding: new[] { 20f, 20f, 20f, 20f });
         var hotel4 = this.CreateTestHotel(hotelId: "key4", embedding: new[] { -1000f, -1000f, -1000f, -1000f });
 
-        using var sut = new CosmosMongoCollection<string, CosmosMongoHotel>(fixture.MongoDatabase, "TestVectorizedSearchWithOffset");
+        using var sut = new CosmosMongoCollection<string, CosmosMongoHotel>(fixture.MongoDatabase, "TestVectorizedSearchWithFilter");
 
         await sut.EnsureCollectionExistsAsync();
 

dotnet/src/IntegrationTests/Connectors/Memory/MongoDB/MongoDBVectorStoreRecordCollectionTests.cs

@@ -389,7 +389,7 @@ public async Task SearchReturnsValidResultsWithFilterAsync()
         var hotel3 = this.CreateTestHotel(hotelId: "key3", embedding: new[] { 20f, 20f, 20f, 20f });
         var hotel4 = this.CreateTestHotel(hotelId: "key4", embedding: new[] { -1000f, -1000f, -1000f, -1000f });
 
-        using var sut = new MongoCollection<string, MongoDBHotel>(fixture.MongoDatabase, "TestVectorizedSearchWithOffset");
+        using var sut = new MongoCollection<string, MongoDBHotel>(fixture.MongoDatabase, "TestVectorizedSearchWithFilter");
 
         await sut.EnsureCollectionExistsAsync();