gh-70363: Implement io.IOBase interface for SpooledTemporaryFile (GH-29560)

Since the underlying file-like objects (either `io.BytesIO`,
or a true file object) all implement the `io.IOBase`
interface, the `SpooledTemporaryFile` should as well.

Additionally, since the underlying file object will either be an
instance of an `io.BufferedIOBase` (for binary mode) or an
`io.TextIOBase` (for text mode), methods for these classes were also
implemented.

In every case, the required methods and properties are simply delegated
to the underlying file object.

Co-authored-by: Gary Fernie <Gary.Fernie@skyscanner.net>
Co-authored-by: Inada Naoki <songofacandy@gmail.com>

Lib/tempfile.py

@@ -639,7 +639,7 @@ else:
             _os.close(fd)
             raise
 
-class SpooledTemporaryFile:
+class SpooledTemporaryFile(_io.IOBase):
     """Temporary file wrapper, specialized to switch from BytesIO
     or StringIO to a real file when it exceeds a certain size or
     when a fileno is needed.
@@ -704,6 +704,16 @@ class SpooledTemporaryFile:
     def __iter__(self):
         return self._file.__iter__()
 
+    def __del__(self):
+        if not self.closed:
+            _warnings.warn(
+                "Unclosed file {!r}".format(self),
+                ResourceWarning,
+                stacklevel=2,
+                source=self
+            )
+            self.close()
+
     def close(self):
         self._file.close()
 
@@ -747,15 +757,30 @@ class SpooledTemporaryFile:
     def newlines(self):
         return self._file.newlines
 
+    def readable(self):
+        return self._file.readable()
+
     def read(self, *args):
         return self._file.read(*args)
 
+    def read1(self, *args):
+        return self._file.read1(*args)
+
+    def readinto(self, b):
+        return self._file.readinto(b)
+
+    def readinto1(self, b):
+        return self._file.readinto1(b)
+
     def readline(self, *args):
         return self._file.readline(*args)
 
     def readlines(self, *args):
         return self._file.readlines(*args)
 
+    def seekable(self):
+        return self._file.seekable()
+
     def seek(self, *args):
         return self._file.seek(*args)
 
@@ -764,11 +789,14 @@ class SpooledTemporaryFile:
 
     def truncate(self, size=None):
         if size is None:
-            self._file.truncate()
+            return self._file.truncate()
         else:
             if size > self._max_size:
                 self.rollover()
-            self._file.truncate(size)
+            return self._file.truncate(size)
+
+    def writable(self):
+        return self._file.writable()
 
     def write(self, s):
         file = self._file
@@ -782,6 +810,9 @@ class SpooledTemporaryFile:
         self._check(file)
         return rv
 
+    def detach(self):
+        return self._file.detach()
+
 
 class TemporaryDirectory:
     """Create and return a temporary directory.  This has the same