Support multi-value options in the CLI

[DaveHanns]

Problem

The CLI has no consistent, framework-level way to accept multiple values for a single flag. The command framework rejects a repeated flag (src/lib/command-framework/apify-command.ts), and there is no built-in comma-separated handling. This blocks flags that mirror API filters typed as string[], for example apify runs ls --status, where the API accepts several statuses.

Goal

Add a framework-wide, opt-in way to declare a flag as multi-value (in the spirit of enableJsonFlag), so commands accept several values consistently.

Convention to decide

Pick one, or support both as gh does:

• Comma-separated: --status a,b
• Repeated flag: --status a --status b

Notes

• Only a couple of flags need this today; the first consumer is apify runs ls --status. The API also supports startedAfter and startedBefore, so runs ls could reach parity.
• Existing single-value flags must keep working unchanged.