feat(chain)!: make KeychainTxOutIndex more range based

`KeychainTxOutIndex` should try and avoid "all" kind of queries.
There may be subranges of interest. If the user wants "all" they can
just query "..".

example-crates/example_electrum/src/main.rs

@@ -210,8 +210,8 @@ fn main() -> anyhow::Result<()> {
             if all_spks {
                 let all_spks = graph
                     .index
-                    .revealed_spks()
-                    .map(|(k, i, spk)| (k, i, spk.to_owned()))
+                    .revealed_spks(..)
+                    .map(|(k, i, spk)| (k.to_owned(), i, spk.to_owned()))
                     .collect::<Vec<_>>();
                 spks = Box::new(spks.chain(all_spks.into_iter().map(|(k, i, spk)| {
                     eprintln!("scanning {}:{}", k, i);