Add IDE support for StringSyntaxAttribute

[CyrusNajmabadi]

Runtime added this attribute in the following PRs:

dotnet/runtime#62995
dotnet/runtime#64063
dotnet/runtime#64081

We will add support in the IDE to detect this attribute and allow it to lightup Regex/DateTime/Json IDE features for string literals used in the right locations.

Note: this applies to fields/properties not just parameters.