Use common definition for FinalizeError
fhdl/autofragment: empty build_fragment by default
fhdl/autofragment: fix submodules
fhdl/tools/flat_iteration: generalize
fhdl/autofragment: remove legacy functions
migen/fhdl/autofragment: factorize
bank/description: AutoReg
bank/csrgen: BankArray
bank/description/AutoReg: check that get_memories and get_registers are callable
fhdl/module: replace autofragment
bus/asmibus: use fhdl.module API
bank/eventmanager: use module and autoreg