Add support for renaming `it`

When you rename `it`, kls currently just apparently does nothing and returns without error.

The expected behaviour would have been to add a lambda parameter with the new name and rename all instances of `it` inside the lambda.

The issue names no file or test, so start by locating the rename-handling entry point for Kotlin lambda expressions and any tests covering renames. Reproduce renaming `it`, then verify that a lambda parameter with the new name is added and every `it` inside that lambda is renamed.

Written by the indexing model from the issue text.