TFT-5021: Raise TMT_REBOOT_TIMEOUT to 1200s for metal boot times

ina vasilevskayarequested to merge
fernflower/infrastructure:raise-tmt-reboot-timeout-metal into main

Bare-metal guests can take well over the tmt default of 600s to come back after a reboot. Set TMT_REBOOT_TIMEOUT to 1200s across the tmt test-schedule configs, matching the TMT_CONNECT_TIMEOUT bump.

Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com

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