Throw an error on unknown frames

[zhiltsov-max]

Motivation and context

Follow up for #1615

Added an exception when frames have invalid ids instead of silently skipping annotations on import.

How has this been tested?

Unit tests

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) 2020 Intel Corporation
#
# SPDX-License-Identifier: MIT

[coveralls]

Pull Request Test Coverage Report for Build 5821

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 65.783%

---

Files with Coverage Reduction	New Missed Lines	%
cvat/apps/engine/media_extractors.py	5	76.18%

Totals
Change from base Build 5815:	0.01%
Covered Lines:	10951
Relevant Lines:	16245

---

💛 - Coveralls

[azhavoro]

Can m or not(0 <= d < self._db_task.data.size) condition be used here?

[zhiltsov-max]

It can, but I'm not a big fan of it. We also could write abs_id in range(start_frame, stop_frame, frame_step).