sts-common-util: add support for UTC ISO date time in UTS_VERSION

These are now supported:

* `2025-07-09T19:15:06Z`
* `2025-07-09T19:15:06+01:30`
* `2025-07-09T19:15:06-09:00`

In particular, the Android Common Kernel now uses an ISO date time in UTS_VERSION:

`#1 SMP PREEMPT 2021-08-28T09:42:03Z`

Bug: 423831250
Bug: 431575108
Change-Id: Ia731fb69ae9334e14765d547542eeb0f21e650fd
2 files changed