…alysis (#130325)

This change removes the duplicate `IObjectNodeWithAlignment` definitions
introduced after #129966 and restores a single shared contract for both
AOT compiler projects.

- **Shared interface**
- Moves `IObjectNodeWithAlignment` to
`src/coreclr/tools/Common/Compiler/DependencyAnalysis/IObjectNodeWithAlignment.cs`
- Uses `namespace ILCompiler.DependencyAnalysis`, matching the
surrounding shared dependency-analysis surface
- Preserves the XML doc contract that `GetAlignment` must stay
consistent with `GetData` / `GetDehydratableData`

- **Project file cleanup**
- Updates `ILCompiler.Compiler.csproj` and
`ILCompiler.ReadyToRun.csproj` to compile the shared Common file
  - Removes the two project-local interface entries

- **Consumer impact**
- ReadyToRun now consumes the shared interface through the common
namespace instead of a project-local duplicate
- Existing implementations continue to compile against a single
definition without changing behavior

```csharp
namespace ILCompiler.DependencyAnalysis
{
    public interface IObjectNodeWithAlignment
    {
        int GetAlignment(NodeFactory factory);
    }
}
```

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: MichalStrehovsky <13110571+MichalStrehovsky@users.noreply.github.com>