[Analyzer Proposal]: Warn on FixedAddressValueType/ThreadStatic on instance fields.

### Background and motivation

The runtime ignores `FixedAddressValueType`/`ThreadStatic` if the field isn't static, this might lead to unexpected GC holes/logic bugs if the programmer doesn't know this.

### API Proposal

Warn on `FixedAddressValueType`/`ThreadStatic` if the field isn't static.

### API Usage

```cs
class C
{
[FixedAddressValueType]
public Int128 S; // Warns
[ThreadStatic]
public int I; // Warns
}
```

### Alternative Designs

See #129664 for discussion about this.

### Risks

_No response_

Start by reading the discussion in #129664 and locate the analyzer entry point responsible for field attributes; no file or test is named in this issue. The work is done when instance fields using FixedAddressValueType or ThreadStatic produce warnings, while static fields do not.

Written by the indexing model from the issue text.