Rafactor: root package models

[ben-mathu]

Part of an ongoing code refactoring to move all models to a common models package.

Fixes #4782

Moved main models to data.models package.

Tested debug on Pixel 4 (Emulator) with API level 30.

[Rishavgupta12345]

contributor review:-

why are you making so many pull requests, you are solving a single issue which is #4782 in parts so make a single branch and merge all your commits in one pull request, it's better than flooding the repository with tons of pull requests. Just keep the repository clean.

[ben-mathu]

Thanks, @ben-mathu Please do make multiple PRs for this issue. Ideally one per package.

This is what I understood from @madhurgupta10 's comment above in issue: #4782 here

[codecov[bot]]

Codecov Report

Merging #4872 (80ea9bd) into master (325a09d) will decrease coverage by 10.83%. The diff coverage is n/a.

:exclamation: Current head 80ea9bd differs from pull request most recent head 36f4193. Consider uploading reports for the commit 36f4193 to get more accurate results

@@              Coverage Diff              @@
##             master    #4872       +/-   ##
=============================================
- Coverage     61.39%   50.55%   -10.84%     
+ Complexity     2786     2218      -568     
=============================================
  Files           338      336        -2     
  Lines         16377    15491      -886     
  Branches       1465     1356      -109     
=============================================
- Hits          10054     7832     -2222     
- Misses         5522     7075     +1553     
+ Partials        801      584      -217     

Impacted Files	Coverage Δ
...ain/java/fr/free/nrw/commons/MediaDataExtractor.kt	18.18% <ø> (-81.82%)	:arrow_down:
...rw/commons/bookmarks/BookmarkListRootFragment.java	91.30% <ø> (-1.62%)	:arrow_down:
...bookmarks/pictures/BookmarkPicturesController.java	100.00% <ø> (ø)
...s/bookmarks/pictures/BookmarkPicturesFragment.java	45.00% <ø> (-22.86%)	:arrow_down:
.../nrw/commons/category/CategoryDetailsActivity.java	63.09% <ø> (-1.54%)	:arrow_down:
.../free/nrw/commons/category/CategoryEditHelper.java	15.78% <ø> (-29.87%)	:arrow_down:
.../fr/free/nrw/commons/category/GridViewAdapter.java	82.85% <ø> (ø)
.../fr/free/nrw/commons/contributions/Contribution.kt	51.28% <ø> (ø)
...w/commons/contributions/ContributionsFragment.java	31.92% <ø> (-23.08%)	:arrow_down:
...mmons/contributions/ContributionsListFragment.java	59.21% <ø> (-17.96%)	:arrow_down:
... and 209 more

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[ben-mathu]

@madhurgupta10 please review