Ensure cleanup() is called for PyEncoders

[radarhere]

In ImageFile, the encoder cleanup() method is not called from Python if there is an error.

Pillow/src/PIL/ImageFile.py

Lines 505 to 520 in 2f2b48d

	e = Image._getencoder(im.mode, e, a, im.encoderconfig)
	if o > 0:
	fp.seek(o)
	e.setimage(im.im, b)
	if e.pushes_fd:
	e.setfd(fp)
	l, s = e.encode_to_pyfd()
	else:
	while True:
	l, s, d = e.encode(bufsize)
	fp.write(d)
	if s:
	break
	if s < 0:
	raise OSError(f"encoder error {s} when writing image file") from exc
	e.cleanup()

However, cleanup() would still be called from _dealloc in C.

Pillow/src/encode.c

Lines 94 to 98 in 2f2b48d

	static void
	_dealloc(ImagingEncoderObject *encoder) {
	if (encoder->cleanup) {
	encoder->cleanup(&encoder->state);
	}

Except that doesn't help a PyEncoder. So this PR ensures cleanup() is called from ImageFile.