fix(no_std): replace std::string with alloc::string for compatibility

Author: Dmenec

crates/chain/src/indexer/keychain_txout.rs

@@ -10,7 +10,7 @@ use crate::{
     spk_txout::SpkTxOutIndex,
     DescriptorExt, DescriptorId, Indexed, Indexer, KeychainIndexed, SpkIterator,
 };
-use alloc::{borrow::ToOwned, vec::Vec};
+use alloc::{borrow::ToOwned, vec::Vec, string::ToString, string::String};
 use bitcoin::{
     key::Secp256k1, Amount, OutPoint, Script, ScriptBuf, SignedAmount, Transaction, TxOut, Txid,
 };
@@ -978,8 +978,8 @@ pub enum InsertDescriptorError<K> {
 fn short_descriptor(
     desc: &Descriptor<DescriptorPublicKey>,
     edge_len: usize,
-) -> std::string::String {
-    let s = std::string::ToString::to_string(desc);
+) -> String {
+    let s = ToString::to_string(desc);
     if s.len() <= edge_len * 2 {
         return s;
     }