Migrate elections-phragmen module storage to proper prefix

[kianenigma]

Currently, the module's data is stored under prefix PhragmenElection, while the version is stored under ElectionsPhragmen. This is also changing with #5678, and will be just additional confusion everywhere to maintain. Move all to a unified prefix.

[gui1117]

This is currently the case with a lot of pallets.

storage version is stored using PalletInfo::name<pallet::Module<..>>() and storages are stored after a fixed prefix declared in decl_storage and instances.

All this will be solved by macro attribute as storages will use PalletInfo::name<pallet::Module<..>>() similarly to stored version.

So I guess this issue should be fixed by upgrading pallets to macro attribute once it is merged.

[bkchr]

Yeah, I don't see the reason for this issue?

This is nothing that can be changed from the pallet itself.

[kianenigma]

Indeed, if we move the macro attribute then they will be unified and fixed.

I am not sure if it is noted somewhere: This can cause some migrations to happen by migrating to to attribute macros, which should not be overlooked.

[gui1117]

This can cause some migrations to happen by migrating to to attribute macros, which should not be overlooked.

Yes I wrote it in the upgrade guidelines https://thiolliere.github.io/doc/frame_support/attr.pallet.html#checking-upgrade-guidelines