Use no_run instead of ignore

Use no_run instead of ignore

We have an attribute `no_run` that builds but does not run example code
in Rustdocs, this keeps the examples building as the codebase evolves.

use `no_run` and fix example code so it builds cleanly during test run.

Some examples that require the `electrum` feature to be available have
been feature-gated to make sure they aren't accidentally compiled when
that feature is not enabled.

Co-authored-by: Alekos Filini <alekos.filini@gmail.com>