Add support of the time module in Starlark Processor

[essobedo]

Feature Request

The upstream project starlark-go has added a new module called time to support dates and durations, thus the goal of this feature request is to add the support of this new module in the Starlark Processor.

Desired behavior:

• May want to consider helpers to parse from Telegraf nanosecond int64 to time and back if it's not obvious
• May want to have examples of string parsing and date string formatting
• a demo plugin where we discard metrics older than 2 weeks might be a good demo of its use.

[essobedo]

The corresponding PR #9004

[essobedo]

The ticket to add support of timestamps expressed in nanoseconds google/starlark-go#364