fix: SpkIterator::new_with_range takes wildcards..

fix: SpkIterator::new_with_range takes wildcards..
..into account

When you pass a non-wildcard descriptor in `new_with_range`, we make
sure that the range length is at most 1; if that's not the case, we
shorten it.
We would previously use `new_with_range` without this check and with a
non-wildcard descriptor in `spks_of_all_keychains`, this meant creating
a spkiterator that would go on producing the same spks over and over
again, causing some issues with syncing on electrum/esplora.

To reproduce the bug, run in `example-crates/example_electrum`:
```
cargo run "sh(wsh(or_d(c:pk_k(cPGudvRLDSgeV4hH9NUofLvYxYBSRjju3cpiXmBg9K8G9k1ikCMp),c:pk_k(cSBSBHRrzqSXFmrBhLkZMzQB9q4P9MnAq92v8d9a5UveBc9sLX32))))#zp9pcfs9" scan
```