Disable "Rename Symbol" command for symbols with the `native` flag.

[Scrivener07]

Describe the bug Refactoring a symbol which reaches beyond the current file may do well with some additional checks.

For example, if a user tries to rename an inherited function or event originating from a Base import or other library such as F4SE.

In cases where a refactored symbol's usage originates outside of the current user source folder, then prompt the user with.

The symbol "X" belongs to the import "Y". Are you Sure?

Or something like that to think about.

See also issue #74