.Net: Investigate can we keep constructor for KernelFunction internal

[markwallace-microsoft]

I found not many but a few examples on GitHub of folks implementing ISKFunction:

• FantasyCopilot/src/Services/Services.Desktop/WorkflowService/WorkflowService.Extension.cs at main · Richasy/FantasyCopilot (github.com)
• SemanticKernel.PowerFx/src/SemanticKernel.PowerFx/PowerFxFunction.cs at 96738de2b00b943f76ff3fa8840420d5be7f858d · jorisdg/SemanticKernel.PowerFx (github.com)
• teams-ai/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompt/SKFunctionWrapper.cs at 352b97cc75281418dba6e45824bed12c1193de9a · kevmcdonk/teams-ai (github.com)

How do we feel about these in the context of giving KernelFunction an internal ctor that prevents derivation?

[markwallace-microsoft]

We are going to start by keeping it internal as developers can create custom implementations from any arbitrary method and then they will get the pre/post function hooks support automatically.