Fix resize memory use and image pixels

[zhiltsov-max]

Summary

Closes #618
Closes #607
Closes #606

• Resize is made lazy for images and masks
• Fixed image pixels
• Fixed output image extension - it is now the same as input, if provided
• Added the ext kw-only parameter in Image ctor. It must not be used together with path.

How to test

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2021 Intel Corporation
#
# SPDX-License-Identifier: MIT