Preserve skill selection on character reimport

[mcagnion]

Fixes #8210.
Fixes #8742.

Description of the problem being solved:

When re-importing a character build (especially with "Clear Skills" enabled), Path of Building rebuilds socket groups from imported items/gems but can lose user-selected state for matching groups. This can clear Include in Full DPS, change the active skill selection, or reset multipart / stage / mine sub-state on supported skills.

Steps taken to verify a working solution:

• Preserved a non-default main socket group and active skill on reimport.
• Preserved Include in Full DPS on matching socket groups.
• Preserved disabled active/support gems on reimport.
• Preserved skillPart, skillStageCount, and skillMineCount on supported skills.
• Reimport still completed successfully when socket groups and gems changed.

[mateokladaric]

Fixes #8742 as well

[Wires77]

Looks good, I added a few more things to preserve on re-import. Thanks for adding the tests!