support.logging: add dump_mapseq. dump_seq() cannot display the length of a map() or of a generator expression.

support.logging: add dump_seq.

applet.memory.prom: add verify command.

applet.memory.prom: new applet, replacing memory.27x. The applet has been completely rewritten with a nicer implementation, dramatically improved performance, and support for indirectly addressing memories with many address lines through a shift register.

access.direct.arguments: add support for empty pin sets.

cli: fix analyzer crash on 0-wide fields.

software: add `toolchain` extra for turnkey YoWASP installation.

gateware: fix deprecated construct.

applet.memory.27x: unmark as preview.

applet.memory.27x: increase default read latency to 500 ns. It seems like for some really old EPROMs, like NEC D2732D, 250 ns is not quite enough, and 500 ns would be safer.