Escaping also considers record structs

[SteveDunn]

fix: https://github.com/dotnet/roslyn/issues/74117

Previously, record struct was not considered as needing to be escaped, so types like record struct @decimal would be represented as record struct decimal

[SteveDunn]

I'm not sure if those failures are related to my change, but anyone more familiar with them please correct me if I'm wrong.

[333fred]

@dotnet/roslyn-compiler for a second review.