FIxes improper codec codegen for records declared in referenced projects/assemblies. Roslyn does not guarantee the symbols contain the backing fields for generated properties (see dotnet/roslyn#72374 (comment)) and it also doesn't even report `record struct` symbols as records at all (see dotnet/roslyn#69326).

This makes for a very inconsistent experience when dealing with types defined in external assemblies that don't use the Orleans SDK themselves.

We implement a heuristics here to determine primary constructors that can be relied upon to detect them consistently:
1. A ctor with non-zero parameters
2. All parameters match by name exactly with corresponding properties
3. All matching properties have getter AND setter annotated with [CompilerGenerated].

In addition, since the backing field isn't available at all in these records, and the corresponding property isn't settable (it's generated as `init set`), we leverage unsafe accessors (see https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.unsafeaccessorattribute?view=net-8.0) instead. The code checks whether the `FieldAccessorDescription` has an initializer syntax or not to determine whether to generate the original code or the new accessor version.

The signature of the accessor matches the delegate that is generated for the regular backing field case, so there is no need to modify other call sites.

Fixes dotnet#9092

In externally defined symbols, we need to also check for `[CompilerGenerated]`.

This allows running F5 on the generator project and troubleshoot issues. By checking for an already attached debugger, we can debug also scenarios of code generation where the roslyn component starts it with DTB=true.