gateware: add compressed ila, update luna/usb dependencies

[vk2seb]

• Switch to latest eurorack-pmod libraries with some timing fixes (s/clk_fs/fs_strobe)
• Rebase Iso work on top of latest LUNA (has some bugfixes)
• Vendor in the ILA from LUNA, modify it such that we only store waveform changes (basic RLE-like compression). This is important for being able to see audio signals at a 60Mhz system clock.
• Update the USB audio example to import some changes from upstream work
• Add optional ILA build to USB audio example (I used it to debug sample rate feedback).