Collection Expression like condition syntax (with `in` / `not in` csharp-y idioms)

### Summary

Introduce support for collection-based condition expressions in MSBuild, such as `$(TargetOS) not in ['browser', 'haiku', 'illumos']`, to simplify and clarify multi-value comparisons.

### Background and Motivation

MSBuild currently requires verbose chaining of `and`/`or` conditions to check if a property matches (or doesn't match) a set of values. This becomes unwieldy and error-prone, especially in cross-platform builds or SDK logic where exclusion lists are common.

Example today:

```xml
Condition="'$(TargetOS)' != 'browser' and '$(TargetOS)' != 'haiku' and '$(TargetOS)' != 'illumos' and '$(TargetOS)' != 'netbsd' and '$(TargetOS)' != 'solaris'"
```
This is hard to read, maintain, and scale.

There are several cases in the runtime repo (e.g., [this one](https://github.com/dotnet/runtime/pull/117953#discussion_r2226086592)) where this change can significantly reduce code length.

### Proposed Feature

Enable syntax like:
```xml
Condition="'$(TargetOS)' not in ['browser', 'haiku', 'illumos', 'netbsd', 'solaris']"
```

or:
```xml
Condition="!['browser', 'haiku', 'illumos', 'netbsd', 'solaris'].Contains('$(TargetOS)')"
```

This would improve clarity and reduce duplication in build logic.

### Alternative Designs

Allow item groups in conditions with .Contains():

```xml

<_NativeAotSupportedOS Condition="!@(UnsupportedOS->'%(Identity)').Contains('$(TargetOS)')">true

```

This works but is verbose and not usable inline in many contexts.