Refactor `fun isPairPropertyBackingField` using `PSI`

[diphtongue]

What's done:

• fun isPairPropertyBackingField using PSI

Closes #1822

[github-actions[bot]]

JUnit Tests (macOS, EnricoMi/publish-unit-test-result-action@v2)

   164 files  ±0     164 suites  ±0   4m 30s :stopwatch: -26s 1 413 tests ±0  1 377 :heavy_check_mark: ±0  36 :zzz: ±0  0 :x: ±0  2 792 runs  ±0  2 756 :heavy_check_mark: ±0  36 :zzz: ±0  0 :x: ±0 

Results for commit 5abb49bd. ± Comparison against base commit bb237432.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

JUnit Tests (Windows, EnricoMi/publish-unit-test-result-action@v2)

   164 files  ±0     164 suites  ±0   7m 4s :stopwatch: -6s 1 413 tests ±0  1 396 :heavy_check_mark: ±0  17 :zzz: ±0  0 :x: ±0  2 792 runs  ±0  2 775 :heavy_check_mark: ±0  17 :zzz: ±0  0 :x: ±0 

Results for commit 5abb49bd. ± Comparison against base commit bb237432.

:recycle: This comment has been updated with latest results.

[codecov[bot]]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (bb23743) 78.44% compared to head (5abb49b) 78.39%.

Files	Patch %	Lines
...m/saveourtool/diktat/ruleset/utils/AstNodeUtils.kt	61.53%	0 Missing and 5 partials :warning:
...t/ruleset/rules/chapter6/CustomGetterSetterRule.kt	0.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1857 +/- ## ============================================ - Coverage 78.44% 78.39% -0.06% - Complexity 2455 2456 +1 ============================================ Files 133 133 Lines 8644 8645 +1 Branches 2184 2184 ============================================ - Hits 6781 6777 -4 - Misses 896 898 +2 - Partials 967 970 +3 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.