Move Rust API unit tests to a separate directory

[vinnamkim]

Summary

• Ticket no. 127586
• It comes from this feedback, Develop JsonSectionPageMapper in Rust API #1224 (comment).

How to test

$ cd rust
$ cargo test

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

All modified and coverable lines are covered by tests ✅

Comparison is base (6b567b7) 80.44% compared to head (049d952) 80.44%.
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1227   +/-   ##
========================================
  Coverage    80.44%   80.44%           
========================================
  Files          269      269           
  Lines        29915    29915           
  Branches      5850     5850           
========================================
  Hits         24066    24066           
  Misses        4487     4487           
  Partials      1362     1362           

Flag	Coverage Δ
macos-11_Python-3.8	79.10% <ø> (ø)
ubuntu-20.04_Python-3.8	80.44% <ø> (ø)
windows-2022_Python-3.8	80.41% <ø> (ø)

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[wonjuleee]

Thank you for the quick update.