EnC: Emit array and UTF8 literals using FieldRva

[tmat]

Currently disabled since updating FieldRva tables is not supported by the runtime.
We would need to define what the RVA points to in metadata delta (perhaps the Blob heap)?

The compiler emits unoptimized array initialization, which might result in large IL.

Issue referred to from tests and comments.

Required to support C# 14 feature: https://github.com/dotnet/roslyn/blob/main/docs/features/string-literals-data-section.md