Follow-up to #47208.

`UnrecognizedCommandError` calls `printing_commands` to make "Did you
mean?" suggestions.  `printing_commands` calls `RakeCommand::rake_tasks`,
which loads the Rake tasks if they have not been memoized.  If the tasks
have already been loaded by `RakeCommand::perform` (but not memoized by
`RakeCommand::rake_tasks`), then the tasks will be loaded a second time.
This can cause, for example, constant redefinition warnings if the task
files define constants.

Therefore, this commit memoizes the tasks from `RakeCommand::perform`
before raising `UnrecognizedCommandError`.