Cardano Updates

feat(scripts): add rm_retry for robust directory removal

Introduce the rm_retry function in common.sh to improve reliability when
removing directories, especially in container environments where "directory
not empty" errors may occur. Update start-cluster scripts to use rm_retry
instead of direct rm -rf calls, retrying removal up to 5 times before
failing.

refactor(common.sh): improve argument handling and clarity

- Use local variables with descriptive names for target era and epoch in
  wait_for_era and wait_for_epoch functions, adding error messages for
  missing arguments.
- Replace positional parameter usage with named variables for better
  readability and maintainability.
- Add local variable declaration for loop variable in check_spend_success
  and wait_for_era to avoid polluting global scope.

fix(instance): clarify delay vs in-use error handling

Improve error messages and logic for handling delayed instances versus
instances already in use. Now, attempting to use a delayed instance
provides a clearer message and returns an error, while the distinction
between "in use" and "delayed" is made explicit in both logs and flow.