Move read_to_end out of util module

The `read_to_end` function is only used in the `psbt` module, move it
there.

Done as part of work trying to flatten the `util` module.

bitcoin/src/util/mod.rs

@@ -13,24 +13,6 @@ pub mod base58;
 pub mod psbt;
 pub mod taproot;
 
-use crate::prelude::*;
-use crate::io;
-
-// core2 doesn't have read_to_end
-pub(crate) fn read_to_end<D: io::Read>(mut d: D) -> Result<Vec<u8>, io::Error> {
-    let mut result = vec![];
-    let mut buf = [0u8; 64];
-    loop {
-        match d.read(&mut buf) {
-            Ok(0) => break,
-            Ok(n) => result.extend_from_slice(&buf[0..n]),
-            Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {},
-            Err(e) => return Err(e),
-        };
-    }
-    Ok(result)
-}
-
 /// The `misc` module was moved and re-named to `sign_message`.
 pub mod misc {
     use crate::prelude::*;

bitcoin/src/util/psbt/raw.rs

@@ -14,7 +14,6 @@ use crate::io;
 use crate::consensus::encode::{self, ReadExt, WriteExt, Decodable, Encodable, VarInt, serialize, deserialize, MAX_VEC_SIZE};
 use crate::hashes::hex;
 use crate::util::psbt::Error;
-use crate::util::read_to_end;
 
 /// A PSBT key in its raw byte form.
 #[derive(Debug, PartialEq, Hash, Eq, Clone, Ord, PartialOrd)]
@@ -173,3 +172,18 @@ where
         Ok(deserialize(&key.key)?)
     }
 }
+
+// core2 doesn't have read_to_end
+pub(crate) fn read_to_end<D: io::Read>(mut d: D) -> Result<Vec<u8>, io::Error> {
+    let mut result = vec![];
+    let mut buf = [0u8; 64];
+    loop {
+        match d.read(&mut buf) {
+            Ok(0) => break,
+            Ok(n) => result.extend_from_slice(&buf[0..n]),
+            Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {},
+            Err(e) => return Err(e),
+        };
+    }
+    Ok(result)
+}