[RSDK-8761] - Use ISO datetime format

[seanavery]

Description

Currently, I am using a non standard datetime format YYYY-MM-DD_HH-MM-SS which I adopted from FFmpeg segment examples.

To make the DoCommand endpoint easier to use, this PR moves to standard ISO 8601 format YYYY-MM-DDTHH:MM:SS.

golang:

• golang does not support standard ISO 8601, rather, it uses RFC 3339 which includes the timezone.
  • It is not possible for the strftime formatter in FFmpeg to match this.

python:

Testing

• storage ✅
• save ✅
• fetch ✅