a solution should be found for hardfork and upgrading

[vang1ong7ang]

the hardfork coding style is introduced because it's necessary for neo to ensure the safety when upgrading (see #2910 and #3233)

but it's not a good solution in my opinion

1. developers struggle to adhere to the current hardfork coding style
2. the increasing number of HF_XXXs complicates code maintenance and introduces critical risks during future upgrades
3. it slows down the process of applying hotfixes to the Neo core. For example, if many changes are based on an upcoming HF_DEFG and a critical bug requires an urgent hotfix, this can lead to conflicts with HF_DEFG