`_TransformWebConfig` target should not run if `IsPublishable` is `false`

### Describe the bug
The `_TransformWebConfig` target shouldn't run on `dotnet publish` when `IsPublishable` is set to false.

The below example is slightly contrived as it doesn't make sense to run dotnet publish on a single project with `IsPublishable` set to false, but this scenario can be hit if you have a solution with multiple projects, and one of those has `IsPublishable` set to false.

### To Reproduce
I can reproduce this on both 10 preview 6, and 8.0.404.

1. `dotnet new web`
2. `dotnet publish /p:IsPublishable=false -bl`

Expected results: should be able to run publish and have it be a no op.

Actual Results: _TransformWebConfig task tries to run, and fails due to missing files (see error below)

### Exceptions (if any)
```
C:\Program Files\dotnet\sdk\10.0.100-preview.6.25358.103\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:
The "TransformWebConfig" task failed unexpectedly.
System.IO.DirectoryNotFoundException: Could not find a part of the path 'C:\Temp\new\bin\Release\net10.0\publish\w
eb.config'.
at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, Fil
eShare share, FileOptions options)
at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare
share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare sha
re, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, Fil
eShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
at System.IO.FileStream..ctor(String path, FileMode mode)
at Microsoft.NET.Sdk.Publish.Tasks.TransformWebConfig.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(TaskExecutionHost taskExecutionHost, TaskLogging
Context taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask)
```

### Further technical details

```
.NET SDK:
Version: 10.0.100-preview.6.25358.103
Commit: 75972a5ba7
Workload version: 10.0.100-manifests.6616851e
MSBuild version: 17.15.0-preview-25358-103+75972a5ba

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22621
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.100-preview.6.25358.103\

.NET workloads installed:
[aspire]
Installation Source: VS 17.14.36301.6
Manifest Version: 8.2.2/8.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.2.2\WorkloadManifest.json
Install Type: Msi

Configured to use workload sets when installing new manifests.
Workloads are configured to install and update using workload versions, but none were found. Run "dotnet workload restore" to install a workload version.

Host:
Version: 10.0.0-preview.6.25358.103
Architecture: x64
Commit: 75972a5ba7

.NET SDKs installed:
6.0.428 [C:\Program Files\dotnet\sdk]
8.0.412 [C:\Program Files\dotnet\sdk]
9.0.107 [C:\Program Files\dotnet\sdk]
9.0.205 [C:\Program Files\dotnet\sdk]
9.0.302 [C:\Program Files\dotnet\sdk]
10.0.100-preview.6.25358.103 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.0-preview.6.25358.103 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.0-preview.6.25358.103 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.0-preview.6.25358.103 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

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

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