Default staged skills to their maximum stages

[OursCodeur]

Fixes: requested feature backlog - Max stages of skills by default.

Description of the problem being solved:

Stage-based skills default to 1 stage unless the user changes them manually. This makes staged skills show a lower-than-expected default state in both the Skills UI and calculations.

This change stores each active skill's resolved maximum stage count and uses that as the default when no explicit stage count has been set.

Note: this applies when the skill is usable. Skills that are currently unusable because of weapon requirements still behave as they do today until a valid weapon is equipped.

Steps taken to verify a working solution:

• Verified 40ish skills including Flameblast of Celerity, Incinerate of Venting, Blade Blast, Blight and Blight of Contagion, Reave and Vaal Reave, Scorching Ray, Penance Brand of Dissipation, Wintertide Brand, Scourge Arrow, Tornado of Elemental Turbulence...
• Verified Blade Flurry and Thunderstorm update to their max stages once a valid weapon is equipped.

Implementation TLDR

While querying the skill details to set the multiStage flag, the max stage value is now parsed and stored in a new stagesMax skillData variable and used in the UI where relevant.

Skills UI

Calcs Tab

Behaviour without / with usable weapon