Code cleanup of SiSpacePointsSeedTool_xk package (ATLASRECTS-3037)

Code cleanup of SiSpacePointsSeedTool_xk package

• Define enums to remove magic numbers.
• Use constexpr.
• Use object vectors instead of pointer arrays.
• Avoid new and delete.
• Use default destructor.

The corresponding changes for SiSpacePointsSeedMaker_ATLxk will be done by MR !23244 (merged).

This is followup of MR !23186 (merged).