Make Command execute method generic

[25girhese-rbu]

Introduce a generic execute signature () on Command and parameterize AbstractCommand with T to allow commands to return specific ScmResult subtypes. Update AbstractCheckOutCommand to extend AbstractCommand and adjust its execute/executeCommand signatures accordingly. Adapt GitCheckOutCommand to the new checkout API: use the new executeCheckOutCommand params, rename repository to gitRepo, remove legacy binary/forceBinary handling, add recursive clone flag, and update clone/pull/checkout/list command invocations. Add success_build.log and apply minor comment/formatting tweaks.

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[kwin]

Isn’t this covered in #1273?