C#: JSII cannot infer type for IDictionary

### Describe the bug

When LINQ method `ToDictionary()` is used, it returns a dictionary, that is described by reflection as `IDictionary<,>`. When this type is used as a parameter for `BuildSpec.FromObject()`, JSII runs in to problems to recognize correct type throwing `ArgumentException`:

```
System.ArgumentException: Could not infer JSII type for .NET type 'IDictionary`2' (Parameter 'type')
```

### Expected Behavior

Method `BuildSpec.FromObject()` is described in C# implementation of CDK as:

```
public static BuildSpec FromObject(IDictionary value)
```

I would expect one of two things in this case:

- JSII can handle interface type.
- C# implementation will not allow to use interface type.

### Current Behavior

Although CDK method is described that it can receive `IDictionary`, argument type cannot be described by C# reflection as interface.

### Reproduction Steps

Pass to the `BuildSpec.FromObject()` any dictionary created through LINQ method `ToDictionary()`.

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### SDK version used

2.121.1

### Environment details (OS name and version, etc.)

Fedora 39

Start by reproducing the failure with a LINQ ToDictionary() result passed to BuildSpec.FromObject(), using the reported SDK version and environment if available. Trace the JSII .NET type-inference path from the IDictionary`2 exception and compare it with the declared IDictionary parameter. Done means the interface type is handled correctly or the public C# signature no longer accepts it, with regression coverage for the reproduction.

Written by the indexing model from the issue text.