Fix selection behaviour on the My Downloads page

[rtibbles]

Summary

• Updates the removeDownloadRequest function to accept a contentnode_id as its only argument (in the process, fixing the latter part of Explore libraries - The option 'Remove from my library' is not positioned correctly and not working #11378)
• Removes duplication in the responsive view of the My Downloads page to make it easier to reason about
• Updates the resource selection to be a map from contentnode_id for the request to true to enable easy lookup in the downloadRequestMap and to be compatible with the updated removeDownloadRequest function
• Adds indeterminate selection determination to the select all checkbox
• Updates deletion setting to use the new map
• Updates checked setting to use the new map

References

Fixes #11389
Fixes #11378 - now that the z-index issue has been fixed by @LianaHarris360

Reviewer guidance

Ensure that all selection behaviour behaves as expected:

• Selecting one should toggle the Select All checkbox to an indeterminate state
• Selections should be preserved across page navigation, but the Select All checkbox state and effect should be scoped to the current page
• Clicking on the Select All checkbox in an indeterminate state will Select All on the page
• Clicking on the Select All checkbox in a checked state will deselect all on the page
• Clicking on the Select All checkbox in an unchecked state will select all on the page
• Table should render properly in smaller screen sizes

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0b6.dev0_git.149.g4b1e3515.pex
Windows Installer (EXE)	kolibri-0.16.0b6.dev0+git.149.g4b1e3515-unsigned.exe
Debian Package	kolibri_0.16.0b6.dev0+git.149.g4b1e3515-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b6.dev0+git.149.g4b1e3515-0.3.0.dmg
Android Package (APK)	kolibri-0.16.0b6.dev0+git.149.g4b1e3515-0.1.0-debug.apk
TAR file	kolibri-0.16.0b6.dev0+git.149.g4b1e3515.tar.gz
WHL file	kolibri-0.16.0b6.dev0+git.149.g4b1e3515-py2.py3-none-any.whl

[pcenov]

@rtibbles I confirm that the selection behaviour is fixed now and the option 'Remove from my library' is functioning.
What puzzles me is that now both 'Remove' and 'Remove selected' are not functioning at all:

2023-10-13_11-29-37.mp4

Also when I remove a resource from the library there is no
snackbar 'Resource removed from my library' as specified in Figma:

2023-10-13_11-37-42.mp4

[rtibbles]

Not terribly confusing - I have clearly messed something up :) Thanks for checking my working.

[rtibbles]

Removal should be working everywhere now, and the snackbar should display when removing a download while browsing a remote library.

[pcenov]

Implemented as specified.

[marcellamaki]

Code changes look good to me, and since this has the Peter stamp of approval, I think we are good to merge. Thanks for the code cleanup and simplification here, @rtibbles :)