Inconsistent casing of Configuration msbuild property when ArtifactsPath is set and unset

### Describe the bug

When the ArtifactsPath property is set the Configuration property is converted to lowercase (EG Debug becomes debug in paths)

https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.DefaultOutputPaths.targets#L57
https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.DefaultOutputPaths.targets#L92

When it is unset the same case set in the configuration definition is used (EG Debug remains Debug in paths).

This bit me when I was trying to work around https://github.com/dotnet/sdk/issues/41530 with a file copy but the inconsistent naming caused issues. I would suggest there should be a singular approach to casing rather than two.

### To Reproduce

```
dotnet build --configuration "Debug"
```

will produce bin/Debug in project folders

```
dotnet build --configuration "Debug" --artifacts-path build-output
```

will produce build-output/bin//debug

### Exceptions (if any)

### Further technical details

```
.NET SDK:
Version: 8.0.110
Commit: 87a66bb3d1
Workload version: 8.0.100-manifests.9143487c

Runtime Environment:
OS Name: ubuntu
OS Version: 22.04
OS Platform: Linux
RID: ubuntu.22.04-x64
Base Path: /usr/lib/dotnet/sdk/8.0.110/

.NET workloads installed:
Workload version: 8.0.100-manifests.9143487c
There are no installed workloads to display.

Host:
Version: 8.0.10
Architecture: x64
Commit: 81cabf2857

.NET SDKs installed:
8.0.110 [/usr/lib/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.10 [/usr/lib/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.10 [/usr/lib/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
None

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download
```

Workaround for anyone else who runs into this without being able to apply the patch to set artifact path via CLI if you define the property via msbuild (eg in a Directory.build.props)

```

$(MSBuildThisFileDirectory)\build-output

```

dotnet restore restores in the right place and uses the lowercase configuration in the path so at least all the commands produce consistent output.