Apply minor internal improvements

[keram]

• Use idris-notes-buffer-name variable in idris-commands.el
• Remove unused idris-hole-list-buffer-visible-p
• Remove Idris event logging and custom history file from make test3
  • Use idris-repl-buffer-name instead of (idris-buffer-name :repl
  • Use idris-process-buffer-name instead of (idris-buffer-name :process)
  • Use idris-connection-buffer-name instead of (idris-buffer-name :connection)

Why: To improve maintainability