POC for emitting record struct-like types (for use in PowerShell)

C# 10.0 (currently in preview) introduces value-type records (record struct) as a native part of the language syntax.

In reality, record struct is just a macro for generating structs with a constructor that takes all members as arguments and provides safe implementations of IEquatable<T>.Equals(), object.ToString() and a tuple deconstructor - all of which are type traits we can already emit using System.Reflection.Emit.

This POC intends to showcase how an identical type compilation routine could be introduced for emission of record struct-like types in PowerShell.

Much like the existing type emitter in PowerShell, RecordEmitter does the following:

1. Create dynamic assembly at runtime (currently it caches a single static assembly for reuse = name collisions might occur)
2. Define a new struct type (eg. a subtype of System.ValueType)
3. Generate property bindings for all members
4. Generate IL for default get/set routines for each property
5. Generate safe GetHashCode() + object.Equals() overrides based on available members
6. Generate ToString() override + PrintMembers() helper function, to predictably construct meaningful string representations
7. Generate a single public constructor based on member layout
8. Generate tuple deconstructor with signature based on member layout

The following features are currently incomplete or not implemented at all:

• Explicit implementation of IEquatable<T> (the emitter currently generates a safe/correct Equals(T, T) implementation, but the type doesn't declare IEquatable<t> as an implemented interface)
• ToString() override - the heavy lifting is done in PrintMembers(), but no method override currently exists for base.ToString()
• object.Equals(object obj) override is buggy - invoking the type-specific Equals implementation works, but object.Equals(obj) (which is the entry point when using $record -eq $record2 for example) results in invalid IL generation at runtime (likely a problem with argument alignment)
• Deconstructor - record struct results in the generation of a void Deconstruct(out <member1Type> member1, out <member2Type> member2, ..., out <memberNType> memberN) method, not prioritized because of PowerShell's limited use of tuple deconstruction