Change: move timezone init out of print_report_xml_start

[mattmundell]

What

Use a separate function to do the timezone info init for print_report_xml_start.

Why

To make print_report_xml_start easier to maintain.

References

Follows #2653.

Testing

I got a single report with the PR, then got the same report on the main branch. I made sure they were the same. I did that with two timezones just to be sure (using the timezone term in the filter).

o m m '<get_reports report_id="92a09ffd-a5bd-464b-9f2c-54b78ec5ebcf" details="1" filter="timezone=Pacific/Auckland rows=3 apply_overrides=1 min_qod=60"/>' > /tmp/r-auk-main
o m m '<get_reports report_id="92a09ffd-a5bd-464b-9f2c-54b78ec5ebcf" details="1" filter="timezone=Europe/Berlin rows=3 apply_overrides=1 min_qod=60"/>' > /tmp/r-ber-main
diff /tmp/r-auk /tmp/r-auk-main
diff /tmp/r-ber /tmp/r-ber-main

[mattmundell]

Thanks!