`DriverConflict` exception is unhelpful if you use `io.Buffer`

[whitequark]

You get messages like:

amaranth.hdl._ir.DriverConflict: Bit 0 of I/O port (io-port port_a_5__io__io) used twice, at /home/whitequark/Projects/glasgow/software/.venv/lib/python3.12/site-packages/amaranth/vendor/_siliconblue.py:546 and /home/whitequark/Projects/glasgow/software/.venv/lib/python3.12/site-packages/amaranth/vendor/_siliconblue.py:546

It's not completely useless but 2/3 of the information says absolutely nothing.

cc @wanda-phi can we fix this?

[wanda-phi]

... you ever think we need a #[track_caller]?

[whitequark]

Prooooooobably.