Add the history import command (again) (#14083)

# Description

This is mainly https://github.com/nushell/nushell/pull/13450 (which got
reverted). Additionally:
 - always clear IDs on import, disallow specifying IDs when piping
 - added extra tests
 - create backup of the history

# User-Facing Changes

New command: `history import`

# Tests + Formatting

Added mostly integration tests and a few smaller unit tests.

crates/nu-cli/tests/commands/mod.rs

@@ -1,2 +1,3 @@
+mod history_import;
 mod keybindings_list;
 mod nu_highlight;