tests: add some tests of the edge component
edge.comp: fix .out-invert pin on first invocation

Before this commit, edge.*.out and .out_invert would both be 0 after the
first invocation of the component's function.  This commit fixes
.out_invert to always be the inverse of .out.
edge.comp: fix output pulse width

The edge manpage claims that the output pulse width is controllable by
the .out_width_ns parameter, but there's a bug: the output pulse is one
thread period too long.

This commit fixes it.