Fix Herald of Ash overkill damage incorrectly scaling with global damage increases

[Jonathan-Dang]

Calculations fixed, mod inc display edge case issue.

Fixes #8261 .

Description of the problem being solved:

Calculations of Herald of Ash pulled from all sources of Fire damage over time increases, including but not limited to Global Fire damage increases when not supposed to.

Steps taken to verify a working solution:

• Testing with two equipments granting 10% Global Fire Damage and 70% Burning Damage increases and calculated with 40 overkill damage.
• Manual Calculations to confirm number matches changes.
• Only Issue Remains as Inc mods are not filtered. Should open a new issue with this edge case as it far exceeds scope of current issue.

Link to a build that showcases this PR:

https://pobb.in/vwANN9PgixQd

Before screenshot:

After screenshot: