.Net: Plugin name collision resolution mechanism

[SergeyMenshykh]

Context: Today, SK agents add functions returned by AI context providers to a new "Tools" plugin and add that plugin to the kernel plugins. It works fine if kernel plugins don't have a registered plugin with the same name. However, it fails if the "Tools" plugin is already present in the kernel plugins.

To Do: Decide on a way to handle cases like that and apply necessary fixes if needed.