Add in accessibility support for screen readers in board and library managers

[joew46167]

ContributedLibraryTableCellJPanel.java: Add description to accessibility context
ContributedPlatformTableCellJPanel.java: Add description to accessibility context

ProgressJProgressBar.java:
Add status to accessibility context
make progress bar focusable so screen reader can access

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[joew46167]

I clicked Have you written new tests for your core changes, as applicable? but imo it isn't applicable.

[facchinm]

Hi @joew46167 ,
the PR looks fine! Did you have the chance to test it manually with a screen reader? In which platform?
I'm going to merge it immediately to get a broader audience to test it and eventually we can amend it later

[joew46167]

Hi @facchinm

I tested on Windows using NVDA. Ken Perry also tested with