Optimize Python import to make CLI entrypoint faster

[vinnamkim]

Summary

• Ticket no. 123365
• Revise the lazy plugin extra deps checking logic not to import them actually, but just checking their specs (existence).
• Force Environment._get_plugin_exports() not to load classes under datumaro.components.*.
• Introduce datumaro.util.import_util.lazy_import() to import some heavy external modules (e.g., tensorflow, matplotlib, ...) lazily.
• Please see the following results:

1. Before (develop)

(datumaro) (base) vinnamki@vinnamki-mobl:~/datumaro$ time datum -h
...

real    0m11.991s
user    0m11.268s
sys     0m1.906s

2. After (This PR)

(datumaro) (base) vinnamki@vinnamki-mobl:~/datumaro$ time datum -h
...

real    0m1.086s
user    0m1.154s
sys     0m0.751s

How to test

Our existing tests can cover this.

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

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) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (c20dc3e) 80.09% compared to head (8a87f7c) 80.06%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1182      +/-   ##
===========================================
- Coverage    80.09%   80.06%   -0.04%     
===========================================
  Files          267      268       +1     
  Lines        29828    29849      +21     
  Branches      5846     5847       +1     
===========================================
+ Hits         23892    23898       +6     
- Misses        4602     4618      +16     
+ Partials      1334     1333       -1     

Flag	Coverage Δ
macos-11_Python-3.8	79.18% <93.67%> (-0.04%)	⬇️
ubuntu-20.04_Python-3.8	80.06% <97.46%> (-0.03%)	⬇️
windows-2022_Python-3.8	80.03% <97.46%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/datumaro/cli/util/compare.py	20.08% <100.00%> (+0.08%)	⬆️
...o/components/algorithms/hash_key_inference/base.py	84.00% <100.00%> (+0.66%)	⬆️
...ms/noisy_label_detection/loss_dynamics_analyzer.py	84.94% <100.00%> (ø)
src/datumaro/components/environment.py	85.77% <100.00%> (ø)
src/datumaro/components/extractor_tfds.py	95.08% <100.00%> (+1.15%)	⬆️
src/datumaro/components/lazy_plugin.py	91.83% <100.00%> (+0.34%)	⬆️
src/datumaro/components/media.py	79.70% <100.00%> (+0.02%)	⬆️
src/datumaro/components/project.py	79.26% <100.00%> (+0.01%)	⬆️
src/datumaro/components/shift_analyzer.py	91.12% <100.00%> (+0.07%)	⬆️
src/datumaro/components/visualizer.py	88.84% <100.00%> (+0.12%)	⬆️
... and 6 more

... and 2 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[wonjuleee]

Looks very good. Thank you for your efforts.