Now that specialized utimeq module has been implenented, revert previous
adhoc changes to uheapq.

This reverts commit 0cbc0722.

So that one can easily access the underlying data of the frame buffer, eg
to write the data out to a display.

If the destination of os.rename() exists then it will be overwritten if it
is a file.  This is the POSIX behaviour, which is also the CPython
behaviour, and so we follow suit.

See issue #2598 for discussion.

For backwards compatibility.  It simple creates a frame buffer with the
MVLSB format.

Rename FrameBuffer1 into FrameBuffer and make it handle different bit
depths via a method table that has getpixel and setpixel.  Currently
supported formats are MVLSB (monochrome, vertical, LSB) and RGB565.

Also add blit() and fill_rect() methods.

As required for further elaboration of uasyncio, like supporting baremetal
systems with wraparound timesources. This is not intended to be public
interface, and likely will be further refactored in the future.

Otherwise this broke esp8266 testsuite.

As per CPython semantics.  In particular, file.__del__() should not raise
an exception if the file is already closed.

Covered case:
- Stat cases
- Invalid read/write/flush/close
- Invalid mkdir/rmdir/remove/getcwd
- File seek/tell, modes a/x/+, t/b
- Writing to a full disk
- Full path rename, slash trim
- Rename cases
- Bytestring listdir
- File object printing

Try to un-mount a file system and re-mount it again.