Support any name for a manifest

[Marishka17]

Motivation and context

Resolve #3968

• Added support for uploading a manifest with any name
• Added manifest structure validation

How has this been tested?

Manually

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]

@Marishka17 Hi, please also don't forget to update backup functionality as well https://github.com/openvinotoolkit/cvat/blob/develop/cvat/apps/engine/backup.py#L261

[Marishka17]

@Marishka17 Hi, please also don't forget to update backup functionality as well https://github.com/openvinotoolkit/cvat/blob/develop/cvat/apps/engine/backup.py#L261

@azhavoro, Right now I'm not sure that I need to update it because the name manifest.jsonl will be used inside CVAT part.