Rationalize behavior of `TestItemsWithUnexpandableMetadata`

Reenable the test `TestItemsWithUnexpandableMetadata`
https://github.com/dotnet/msbuild/blob/46b723ba9ee9f4297d0c8ccbb6dc52e4bd8ea438/src/Build.UnitTests/ConsoleLogger_Tests.cs#L324

Build this project:

```xml

a\b\%(Filename).c

```

The diag console logger currently prints:
```
Initial Items:
F
-in "x\y\z"
MetadataFileName = Cannot expand metadata in expression "a\b\%(Filename).c". The item metadata "%(Filename)" ca
nnot be applied to the path "-in "x\y\z"". Illegal characters in path.
```

The logger in unit-test `TestItemsWithUnexpandableMetadata` currently prints:
```
Initial Items:
F
-in "x\y\z"
MetadataFileName = a\b\%(Filename).c
```

And I don't know why, nor do I know which behavior is better.