artiq_coremgmt: improve logging when flashing

[SimonRenblad]

Uses logging module in artiq_coremgmt, and adds additional logging when running artiq_coremgmt flash.

Example output of artiq_coremgmt -vv flash ...:

INFO:__main__:Retrieving binaries...
DEBUG:artiq.frontend.flash_tools:converting gateware bit file to bin
DEBUG:artiq.frontend.flash_tools:Design: top;COMPRESS=TRUE;UserID=FFFFFFFF;Version=2024.2
DEBUG:artiq.frontend.flash_tools:Part name: 7a100tfgg484
DEBUG:artiq.frontend.flash_tools:Date: 2025/08/07
DEBUG:artiq.frontend.flash_tools:Time: 15:21:14
DEBUG:artiq.frontend.flash_tools:Bitstream payload length: 0x2bc888
INFO:__main__:Flashing core device...
DEBUG:artiq.coredevice.comm_mgmt:sent 1 bytes
DEBUG:artiq.coredevice.comm_mgmt:sending message: type=<Request.Flash: 9>
DEBUG:artiq.coredevice.comm_mgmt:sent 1 bytes
DEBUG:artiq.coredevice.comm_mgmt:writing /tmp/nix-shell.EvDsLr/artiq_pdcn6b2g_top.bit to byte buffer
DEBUG:artiq.coredevice.comm_mgmt:writing artiq_kasli/minimal/software/bootloader/bootloader.bin to byte buffer
DEBUG:artiq.coredevice.comm_mgmt:writing artiq_kasli/minimal/software/runtime/runtime.fbi to byte buffer
DEBUG:artiq.coredevice.comm_mgmt:sending byte buffer to core device
DEBUG:artiq.coredevice.comm_mgmt:sent 4 bytes
DEBUG:artiq.coredevice.comm_mgmt:sent 4886580 bytes
DEBUG:artiq.coredevice.comm_mgmt:receiving message: type=<Reply.RebootImminent: 3>
INFO:__main__:Rebooting core device.