Nullness issue - show C# nullness attributes in tooltips

[T-Gro]

Issue description

F# does not support flow analysis and (attributes built around it)[https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/nullable-analysis], such as:
NotNullIfNotNull
NotNullWhen

Even though F# compiler will not interpret them, they are still a relevant source of information.
Especially, they can indicate when it is safe to ignore a warning, or unsafely convert a value via Unchecked.nonNull

Choose one or more from the following categories of impact

• Unexpected nullness warning (false positive in nullness checking, code uses --checknulls and langversion:preview).
• Missing nullness warning in a case which can produce nulls (false negative, code uses --checknulls and langversion:preview).
• Breaking change related to older null constructs in code not using the checknulls switch.
• Breaking change related to generic code and explicit type constraints (null, not null).
• Type inference issue (i.e. code worked without type annotations before, and applying the --checknulls enforces type annotations).
• C#/F# interop issue related to nullness metadata.
• Other (none of the categories above apply).

Operating System

Windows (Default)

What .NET runtime/SDK kind are you seeing the issue on

.NET SDK (.NET Core, .NET 5+)

.NET Runtime/SDK version

No response

Reproducible code snippet and actual behavior

No response

Possible workarounds

No response