Fix assembly not found on Android in Debug configuration

[mattjohnsonpint]

Noticed that when building an Android app in debug configuration, with Sentry debugging on, I was seeing failures reading the assembly to create debug info:

Debug: Creating SentryStackTrace. isCurrentStackTrace: False.
Debug: Couldn't find assembly /data/data/com.companyname.mymauiapp/files/.__override__/MyMauiApp.dll in the APK
Debug: Skipping DebugImage for module 'MyMauiApp.dll' because assembly wasn't found: '/data/data/com.companyname.mymauiapp/files/.__override__/MyMauiApp.dll'
Debug: Couldn't find assembly /data/data/com.companyname.mymauiapp/files/.__override__/Microsoft.Maui.Controls.dll in the APK
Debug: Skipping DebugImage for module 'Microsoft.Maui.Controls.dll' because assembly wasn't found: '/data/data/com.companyname.mymauiapp/files/.__override__/Microsoft.Maui.Controls.dll'
Debug: Couldn't find assembly /data/data/com.companyname.mymauiapp/files/.__override__/Microsoft.Maui.dll in the APK
Debug: Skipping DebugImage for module 'Microsoft.Maui.dll' because assembly wasn't found: '/data/data/com.companyname.mymauiapp/files/.__override__/Microsoft.Maui.dll'
Debug: Couldn't find assembly /data/data/com.companyname.mymauiapp/files/.__override__/Mono.Android.dll in the APK
Debug: Skipping DebugImage for module 'Mono.Android.dll' because assembly wasn't found: '/data/data/com.companyname.mymauiapp/files/.__override__/Mono.Android.dll'
Debug: Created DebugStackTrace with 10 frames.

On closer inspection, it looks like assemblies are only embedded in the APK in release mode. In debug mode, they're put on disk as normal files.

Updating the Android assembly reader to use the file on disk if it exists.