Our Portable PDB writer doesn't emit PortableCustomDebugInfoKinds.CompilationOptions

This information is emitted by C#, allowing a compilation to be resurrected from a PDB.

Portable PDB spec is here: https://github.com/dotnet/runtime/blob/main/docs/design/specs/PortablePdb-Metadata.md

It may be useful for F# to emit this information in some situation once we clarify what debugging experience it supports. https://github.com/dotnet/roslyn/blob/3d8acbd585a75e9cdb3509623bf6c39ceb46b2c2/src/Compilers/Core/Portable/PEWriter/MetadataWriter.PortablePdb.cs#L853

• clarify user-facing debug experience this supports
• decide if it's useful for F#
• add code to emit this if it's useful