EnC - Allow capturing new variables in lambdas

[davidwengier]

At the moment we don't allow capturing a variable in a lambda if it wasn't already captured in the baseline compilation. We should consider allowing this, especially in the case where there is already an existing capture of some kind, as the runtime change is a field insert, which is otherwise supported.

This issue is referenced from code.

eg: https://wengier.com/DecompilationDiffer/#5VBNC4JAFJxbEPQflk5KEd0rL0J0qJNBB-kgJhKYQmop4X9vdtPSsFNCh1j27fuaeW8nRYwjQvgQsJAzSuDhhBkG6MNFAIe5mFVTZW7KivJcEBF9oLeBprDnJ5uNPa3DjM_KmL6sJHxz6A2WJueLW2IFMt4Fb8i9rnyXSOm7mDfmGZyvkVf2GrRDrNgf8ET0BUZq7gRbxlYNJzF6-du2LUz2h5wUkckjfqeQUqO1YvDIkDVYKmShogI97vtJ43eFpb5dqFvX9pfKPqrVljam3FpX__5O57rK_6Jxm4pd63gH

[tmat]

Implemented by #70418