Gimlet hot-restart always reprograms FPGA

In theory, we should be able to bounce gimlet_seq without reconfiguring the FPGA (once #650 is merged)

We can test this by restarting gimlet_seq through the debugger:

humility jefe -f gimlet_seq && humility jefe -r gimlet_seq

In practice, I see that the FPGA reports an invalid Ident and Checksum:

 NDX LINE      GEN    COUNT PAYLOAD
   0  122        1        1 Ice40Rails(true, true)
   1  151        1        1 Ice40PowerGoodV1P2(true)
   2  172        1        1 Ice40PowerGoodV3P3(true)
   3  235        1        1 IdentValid(false)
   4  238        1        1 ChecksumValid(false)
   5  241        1        1 Reprogram(true)
   6  255        1        1 Programming
   7  284        1        1 Programmed
   8  287        1        1 RailsOff
   9  290        1        1 Ident(0xde01)
  10  296        1        1 A1Status(0x0)
  11  319        1      446 ClockConfigWrite
  12  327        1        1 ClockConfigSuccess
  13  328        1        1 A2
  14  437        1        7 GetState

This is probably related to the comment

TODO: this may cause trouble with hot restarts, test.

(source)

Start with drv/gimlet-seq-server/src/main.rs around the TODO at lines 122-125, then reproduce the hot restart using the two humility jefe commands in the issue. Trace why the FPGA reports invalid Ident and Checksum values; done means restarting gimlet_seq no longer reprograms an already configured FPGA.