Part of Enhancing Compatibility with runc

There are differences between the events command in runc and youki.

Please refer to the following:
https://github.com/opencontainers/runc/blob/main/man/runc-events.8.md

In runc, options like --interval 1s or --interval 100ms are supported:

runc events testcon --interval 1s

{"type":"stats","id":"testcon","data": ... }

However, in Youki, the --interval argument currently expects a digit-only value:

$ youki events testcon --interval 1s
error: invalid value '1s' for '--interval <INTERVAL>': invalid digit found in string

For more information, try '--help'.

This behavior differs from runc and should be addressed for compatibility.