Adjust temporary files (#5280)

Rigth now it creates something like:
```
.../Perota Chingo/Un viajecito/.12 Rie Chinito.flac64u8gm5u.beets
```
where no separatio between temp name and file extention, and it makes
quite hard to read it.

So, this changes adjust name to
```
.../Perota Chingo/Un viajecito/.12 Rie Chinito.flac.64u8gm5u.beets
```

This was one of forgotten fixup from
8d50301be5

beets/util/__init__.py

@@ -526,7 +526,7 @@ def move(path: bytes, dest: bytes, replace: bool = False):
         dirname = os.path.dirname(bytestring_path(dest))
         tmp = tempfile.NamedTemporaryFile(
             suffix=syspath(b".beets", prefix=False),
-            prefix=syspath(b"." + basename, prefix=False),
+            prefix=syspath(b"." + basename + b".", prefix=False),
             dir=syspath(dirname),
             delete=False,
         )

docs/changelog.rst

@@ -6,6 +6,9 @@ Changelog
 
 Changelog goes here! Please add your entry to the bottom of one of the lists below!
 
+Bug fixes:
+
+* Improved naming of temporary files by separating the random part with the file extension.
 
 2.0.0 (May 30, 2024)
 --------------------