Fix import annotations for frames with dots in name

[sizov-kirill]

Motivation and context

Fixes #2473

How has this been tested?

Unit test

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

[coveralls]

Coverage increased (+0.02%) to 74.079% when pulling b36c5f2 on sk/fix-import-annotations-for-YOLO-format into d2e4ee4 on develop.

[zhiltsov-max]

Why this format is disabled?

[sizov-kirill]

I skipped the test for this format because VGGFace does not support annotations that are generated in the _generate_annotations(...) function. Same problem with ICDAR formats. I can specify annotations for these formats, but this will lead to a lot of code. So I would prefer to remove this test and include images with dots in filename in the test rest api: https://github.com/openvinotoolkit/cvat/blob/4ceb5da2447805c29ca4e20108bb2a2fb31ca6d3/cvat/apps/engine/tests/test_rest_api.py#L2966

[zhiltsov-max]

Actually, the problem I wanted to highlight, was that the reason of skipping was not described in tests. Thus, a reader can't judge, whether this test already can be enabled or not.