[Regression] Wrong naming rules are being enforced for static fields

[davkean]

Version Used:
Works in 15.9, 16.1.2, regressed in 16.2.

Steps to Reproduce:

With this editor config: https://github.com/dotnet/project-system/blob/master/.editorconfig#L112.

Private Shared ReadOnly s_propertyDescriptorCollectionHash As New Hashtable

Expected Behavior:
No errors

Actual Behavior:

Severity	Code	Description	Project	File	Line	Suppression State
Error	IDE1006	Naming rule violation: Missing prefix: '_'	Microsoft.VisualStudio.Editors	E:\project-system2\src\Microsoft.VisualStudio.Editors\ResourceEditor\Resource.vb	273	Active