fix: Adding proguard rules to Sentry.Bindings.Android

[bitsandfoxes]

Resolves #2376
The SDK is looking up the native methods via string. Enabling r8 causes the classes and methods to change.
We're adding the proper rules to the NuGet package to -keep those.
The package structure changes to

.
├── README.md
├── Sentry.Bindings.Android.nuspec
├── [Content_Types].xml
├── _rels
├── build
│   └── net6.0-android31.0
│       └── Sentry.Bindings.Android.targets
├── lib
│   └── net6.0-android31.0
│       ├── Sentry.Bindings.Android.aar
│       ├── Sentry.Bindings.Android.dll
│       ├── Sentry.Bindings.Android.xml
│       ├── sentry-android-core-6.23.0.aar
│       └── sentry-android-ndk-6.23.0.aar
├── package
│   └── services
│       └── metadata
│           └── core-properties
│               └── 27823db434b24f20860179712cee0d5d.psmdcp
├── sentry-nuget.png
└── sentry-proguard.cfg