cli: productionize 'merge-logs'

[knz]

The cockroach debug merge-logs sub-command is not really a "debug" command.

Moreover, with the advent of #48051 we want a general-purpose log editor, and the logic in merge-logs achieves this.

The code should be updated:

• make the "merge-logs" sub-command a non-debug thing, for example cockroach log merge-files
• rename the --to argument to --until, since it's a time boundary
• move the command-line flag initialization from debug.go to flags.go
• enhance the flag description texts
• add new version parser log: implement a crdb-v2 log entry parser and use it in debug merge-logs #65504
• add option to reverse order cli: support reverse order in debug merge-logs #32956
• node ID prefix in output cli: debug merge-logs output should include node id to ensure uniqueness #55395

Jira issue: CRDB-6319

Epic CRDB-20791