Fix newly added trackers being incorrectly all tier 0

[DoubleSpicy]

This PR changes tier of the automatically added trackers to start with existing_max_tier + 1.

In current implementation, tier of additional trackers are initialized with default value 0. To address this, on adding additional trackers, the max tier of existing trackers is looked up and +1 for every additional tracker added.

Closes #20102

Putting 3 testing trackers in "automatically added list" Before: Additional trackers are added with all tier = 0

After: Additional trackers are added with tier after the existing trackers in sequential order.

[DoubleSpicy]

Updated PR to remove accidentally added trailing spaces.

[DoubleSpicy]

ps. I still haven't finished a complete round of review as the new code confuses me.. I'm considering taking the matter on to my hands and submit my revision later.

yup, agree that it is a bit messed up here. Maybe need further discussion on the behavior of tracker tiers beforehand.

[Chocobo1]

Superseded by #20729. Thanks for the effort @DoubleSpicy !