[Analyzers][C#14.0]Raise a notification when an extension method call is redirected to a Span/ReadOnlySpan method

### Is your feature request related to a problem? Please describe.
The new [First-Class Span Types](https://github.com/dotnet/csharplang/issues/7905) feature backfired for me in a couple of scenarios:
* It can [cause](https://github.com/dotnet/csharplang/discussions/9841) a `NullReferenceException` due to a [bug](https://github.com/dotnet/runtime/issues/119901) in the `System.Memory` package
* It also can [cause](https://github.com/dotnet/csharplang/discussions/9841#discussioncomment-15074389) a `VerificationException` ("Operation could destabilize the runtime") in .NET Framework 4.x from a partially trusted domain.

### Describe the solution you'd like
A new analyzer rule could raise a warning ("Possibly unintentional method call" or something like that) when a project targets pre-.NET 10.0 versions, and some extension method call silently switches to another method when the new C# 14.0 features are enabled.

### Additional context
See the links in the bullet points above for more details.