Make function get_progress be compatible with more video format

[Thatwho]

• Add function _get_duration with VideoReader
• Update function get_progress of VideoReader

Motivation and context

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

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

[azhavoro]

@Thatwho Thanks for the your contribution!

[nmanovic]

@Thatwho , should we mention an issue which the PR resolves? Could you please add a line into CHANGELOG.md?

[nmanovic]

@Thatwho , thanks for the contribution!