EXPERIMENT: top/xbeam: 12x12 interface with 2x expanders

[vk2seb]

For context on actually using this, see: #155

Bitstream from above ticket was built with:

TILIQUA_ASQ_I_BITS=2 TILIQUA_ASQ_WIDTH=17 pdm xbeam build --expander-ex0 --expander-ex1 --verbose

Linecount is huge because of the vex reconfig.

Technical details:

• Add gateware for 2 TLQ-EXPANDER pmods to xbeam, rename it to xbeam-ex
• Bump device serial and version so Windows doesn't cache the channel count from xbeam
• Drop tweakable delay lines, drop SoC line rasterizer, shrink vex cache so everything fits in 98% LUTs (!!)
• Add selectable plotting of builtin/ex0/ex1