Accessibility improvements

[vvillenave]

Greetings,
this is a proposal for some accessibility improvements (mainly labelling).
A rather big remaining issue is that the status columns in the TreeView
are still not exposed, and that the context menu for packages still isn’t
accessible through keyboard input. But I’m gonna tackle that another
time hopefully...

[vvillenave]

Guys, any comments on this PR? @mvo5? @BryanQuigley?

[BryanQuigley]

These are generic comments - I'm not using synaptic atm - doing some distro hopping... anyway.. (and wait to see what @mvo5 says before making any big changes)

FIXMEs I would drop all changes to the files you don't think are used any make a separate list of them (and maybe another PR to remove them.

In my limited understanding:
"Accessibility: add proper labelling relations" looks like it really couldn't cause any regressions.
while the other two could potentially cause regressions. - Might be worth separate PRs.

[hamishmb]

I'm not a contributor here, but this looks like a decent set of changes to me. I concur that the labelling seems unlikely to cause any issues.

I'm not sure why the invisible cursor improves accessibility though - I often find it confusing when the cursor isn't visible, especially if I'm controlling a system over eg VNC.