[.NET 6] Big delays in native objects deallocation

### Steps to Reproduce

1. Build the attached sample. The sample shows a window with a "Create Views" button. Every time the button is clicked it creates 1000 instances of a view that contains a NSTextView. The views are not stored anywhere so the expectation is that those views should be GCed.
2. Start the sample using Instruments, with the allocation profiler
3. In Instruments, filter by "NSTextView"
3. Click on the "Create Views" button several times

### Expected Behavior

Every time the button is clicked the NSTextView instance count should be increased by 1000 and then gradually decrease to 0 as the GC starts collecting the views.

### Actual Behavior

This is what I'm experiencing in my machine:

* after the first click 1000 NSTextView instances are created, and none freed.
* after the second click 2000 NSTextView instances are created, and none freed.
* after the third click 1513 NSTextView instances are alive, 1487 freed
* after that, the live instance count keeps growing by 1000 on every click, and freed count stays at 1487
* on the 15th click, the UI freezes and instances start being freed, slowly. The live instance count starts decreasing from around 14000 to 1612. That takes a minute or two, and the UI is completely frozen in that period.

### Environment

```
Visual Studio Community 2022 for Mac Preview
Version 17.0 Preview (17.0 build 5317)
Installation UUID: 756b579c-523c-405c-86c8-c16aec2b68a0

Runtime
.NET 6.0.0-rc.2.21470.23 (64-bit)
Architecture: X64

Roslyn (Language Service)
4.0.0-5.21501.19+8e1779e16298415843e85029d8b52a1ae9bb4c30

NuGet
Versión: 6.0.0.220

.NET SDK
SDK: /usr/local/share/dotnet/sdk/6.0.100-rtm.21521.3/Sdks
Versiones del SDK:
6.0.100-rtm.21521.3
5.0.302
5.0.301
5.0.203
5.0.202
5.0.103
5.0.101
5.0.100
5.0.100-rc.2.20479.15
5.0.100-rc.1.20452.10
5.0.100-preview.5.20279.10
3.1.413
3.1.411
3.1.410
3.1.409
3.1.408
3.1.406
3.1.404
3.1.403
3.1.402
3.1.200
3.1.101
3.1.100
3.1.100-preview3-014645
3.1.100-preview1-014459
3.0.100
3.0.100-rc1-014190
3.0.100-preview9-014004
3.0.100-preview8-013656
3.0.100-preview7-012821
2.2.203
2.2.104
2.1.811
2.1.810
2.1.701
2.1.700
2.1.603
2.1.302
2.1.4
SDK de MSBuild: /usr/local/share/dotnet/sdk/6.0.100-rtm.21521.3/Sdks

.NET Core Runtime
Runtime: /usr/local/share/dotnet/dotnet
Versiones de tiempo de ejecución:
6.0.0-rtm.21518.12
5.0.8
5.0.7
5.0.6
5.0.5
5.0.3
5.0.1
5.0.0
5.0.0-rc.2.20475.5
5.0.0-rc.1.20451.14
5.0.0-preview.5.20278.1
3.1.19
3.1.17
3.1.16
3.1.15
3.1.14
3.1.12
3.1.10
3.1.9
3.1.8
3.1.2
3.1.1
3.1.0
3.1.0-preview3.19553.2
3.1.0-preview1.19506.1
3.0.3
3.0.2
3.0.0
3.0.0-rc1-19456-20
3.0.0-preview9-19423-09
3.0.0-preview7-27912-14
2.2.7
2.2.4
2.2.2
2.1.23
2.1.22
2.1.16
2.1.15
2.1.14
2.1.13
2.1.12
2.1.11
2.1.10
2.1.2
2.0.5

.NET 5.0 SDK
SDK: 5.0.302

SDK de .NET Core 3.1
SDK: 3.1.413

Xamarin.Profiler
Versión: 1.6.15.68
Ubicación: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

Updater
Versión: 11

Xamarin Designer
Version: 17.1.0.1
Hash: 8777be47e
Branch: remotes/origin/main
Build date: 2021-10-21 17:50:43 UTC

Apple Developer Tools
Xcode 12.4 (17801)
Build 12D4e

Xamarin.Mac
Version: 7.11.2.12 (Visual Studio Community)
Hash: 36c9df625
Branch: registrar-never-really-static-on-macos-d16-10-preview2-bumped-mono
Build date: 2021-10-07 14:55:30-0400

Xamarin.iOS
Version: 15.0.0.6 (Visual Studio Community)
Hash: 2771277e0
Branch: xcode13-ios
Build date: 2021-09-23 10:36:08-0400

Xamarin.Android
Versión: 11.3.99.54 (Visual Studio Community)
"Commit": xamarin-android/main/0e5e06f
Android SDK: /Users/lluis/Library/Developer/Xamarin/android-sdk-macosx
Versiones de Android admitidas:
4.4 (nivel de API 19)
4.4.87 (nivel de API 20)
5.0 (nivel de API 21)
5.1 (nivel de API 22)
6.0 (nivel de API 23)
7.0 (nivel de API 24)
7.1 (nivel de API 25)
8.0 (nivel de API 26)
8.1 (nivel de API 27)

Versión de SDK Tools: 26.1.1
Versión de las herramientas de plataforma del SDK: 30.0.5
Versión de las herramientas de compilación del SDK: 30.0.2

Información de compilación:
Mono: c633fe9
Java.Interop: xamarin/java.interop/main@a5ed891
ProGuard: Guardsquare/proguard/v7.0.1@912d149
SQLite: xamarin/sqlite/3.35.4@85460d3
Xamarin.Android Tools: xamarin/xamarin-android-tools/main@683f375

Microsoft OpenJDK for Mobile
Java SDK: /Users/lluis/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_1.8.0.25
1.8.0-25
El código EPL de Android Designer está disponible EPL:
https://github.com/xamarin/AndroidDesigner.EPL

Android SDK Manager
Version: 17.1.0.14
Hash: 9c65d8a
Branch: remotes/origin/HEAD
Build date: 2021-10-21 17:50:45 UTC

Android Device Manager
```

### Build Logs

### Example Project
[Sample.zip](https://github.com/xamarin/xamarin-macios/files/7409494/Sample.zip)