Modify full speed signal gen to remove the DDSs for baseband pulses generation and save BRAM resources

[ghost]

Updated signal_gen_v6 with 2 parameters:

• GEN_DDS to enable/disable DDS generation (saves 32 BRAM per gen)
• ENVELOPE_TYPE to select if envelope table is Real or Complex (cuts envelope BRAM in half)

Created 16full-speed channels project in https://github.com/openquantumhardware/qick_fw_misc/tree/main/qick_tprocv2_216_rfbv2_16fullspeed

[meeg]

• QickConfig.description() was accessing QickSoc attributes, which breaks Pyro - changed to use the QickConfig dictionary
• the check for complex envelopes in load() was using np.isreal(), which doesn't do the job - changed to check that the Q values are zero
• added a complex-envelopes check in add_envelope() - we want to validate programs on the user side before they get pushed to the board
• undo some changes to how hierarchies are handled in _get_block(), clean up map_signal_paths() instead
• general cleanup of generator driver classes
• the checks for unsupported pulse parameters in asm_v2.py were incomplete
• added similar checks for asm_v1.py

The demo firmware is https://s3df.slac.stanford.edu/people/meeg/qick/tprocv2/2025-06-11_216_tprocv2r23_rfbv2_16fullspeed/.

[ghost]

@meeg is it ready to merge? do you want me to check something on my side before?