Replace react-mosaic with mirador-mosaic

[cbeer]

This PR replaces react-mosaic, a 3rd party library for managing the mosaic window layout, with a custom mirador-mosaic window manager.

This work was initially started out of necessity (react-mosaic did not support newer versions of react-dnd, blocking us from upgrading to new versions of react). react-mosaic 6.x was released with that support, so this is no longer an upgrade blocking issue, but may address some of the UX and usability feedback:

UM

Rearranging the windows is challenging (Issue #1)

• When attempting to rearrange the windows within the Mosaic workspace, it was difficult for participants to get the windows in the arrangement they wanted and then to expand or contract the window width to make each window equal.
• Make the frame of each window more visually apparent and grabbable/draggable to allow for easier re-sizing

mirador-mosaic also opens up some opportunities for pre-canned layouts specified using css grids (although that work was not done in this PR):

• Consider having some of the more common layouts (ex: vertical columns, 2x2 boxes) offered as menu options

Kapture.2023-02-22.at.10.33.22.mp4

TODO:

• mouseover styling for window frame borders
• visual feedback when borders "snap"
• path for migrating WorkspaceMosaic layouts to WorkspaceGrid
• user testing?
• implement custom drag layer for prettier drag previews? (in particular, making sure that surrounding content isn't picked up as part of the browser native preview)
• actually calculate the drag/drop area sizes to give a more accurate preview

[codecov-commenter]

Codecov Report

Merging #3640 (afbb72c) into master (2c2f553) will decrease coverage by 0.20%.
The diff coverage is 44.44%.

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@@            Coverage Diff             @@
##           master    #3640      +/-   ##
==========================================
- Coverage   88.92%   88.73%   -0.20%     
==========================================
  Files         200      200              
  Lines        3430     3372      -58     
==========================================
- Hits         3050     2992      -58     
  Misses        380      380              

Impacted Files	Coverage Δ
src/components/AppProviders.js	91.30% <ø> (ø)
src/components/SearchResults.js	100.00% <ø> (ø)
src/components/Workspace.js	95.83% <0.00%> (-4.17%)	⬇️
src/components/WorkspaceSelectionDialog.js	93.75% <0.00%> (-6.25%)	⬇️
src/config/settings.js	0.00% <ø> (ø)
src/state/reducers/rootReducer.js	100.00% <ø> (ø)
src/components/WorkspaceGrid.js	14.28% <14.28%> (ø)
src/state/reducers/gridLayout.js	66.66% <66.66%> (ø)
src/components/SearchHit.js	100.00% <100.00%> (ø)
src/components/Window.js	83.33% <100.00%> (+8.33%)	⬆️
... and 1 more

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