applet.yamaha_opl: document choice of MCLK frequency. NFC.

applet.yamaha_opl: simplify. NFC.

applet.jtag: separate IR/IDCODE scan from segmentation. This allows for much cleaner and robust code. This commit also fixes an issue where 0→1 transitions would also cause the IR segmentation code to split off an IR, even though such a transition is not legal at the start of an IR.

applet.jtag: scan: improve output for complex chains. Before this commit, if automatic IR segmentation fails, nothing useful would be shown. After this commit, the IDCODEs are shown, and IR and DR values are also shown for debugging.

applet.jtag_pinout: fix a confusing message.

applet.yamaha_opl: web: add YM3526 support.

applet.yamaha_opl: web: clean up player queueing.

applet.yamaha_opl: try to enable missing features. This may (or may not) work around some VGM bugs.

README: update to account for ECP5 RE effort.

hardware: make Fab layers more readable