Auto-install latest/official kiwix-tools + tighten up code

[holta]

Instead of IIAB having to hard-code and host a new version of kiwix-tools every month or so:

1. This makes installing the lastest/official kiwix-tools release automatic, based on Kiwix's permalink redirects:
   • https://www.kiwix.org/en/downloads/kiwix-serve/
   • REQUEST: Permalink to latest nightly builds — for QA/CI pipelines ! kiwix/k8s#50
2. Bonus it's now easier to quickly update to the very latest official kiwix-tools release (if any IIAB implementer wants that pre-flight / pre-deployment). It's now as easy as running:

   cd /opt/iiab/iiab
   sudo ./runrole --reinstall kiwix
   

3. Specific versions of kiwix-tools can now be hard-coded even more easily than in the past, by hand editing /opt/iiab/iiab/roles/kiwix/defaults/main.yml that explains your options much more clearly — e.g. during regression testing (progress testing!) comparing different versions of kiwix-tools, etc.

RECAP: As usual, this installs kiwix-tools' 3 executables {kiwix-manage, kiwix-search, kiwix-serve} into /opt/iiab/kiwix/bin but does it in a more compact and automated way than in the past.

Tested on Ubuntu 22.10 (pre-release).

Not a big deal, but a Caveat: downloading of kiwix-tools will occasionally now take a bit longer (e.g. sometimes a full minute) as Kiwix download mirrors can be quite scattershot. These inconsistent results appear to be luck of the draw (very random) from my experience, probably based Kiwix's "round robin" mirror server rotation that's quite a familiar issue over recent years.

Building on:

• PR kiwix-tools 3.3.0 is coming very soon (with "opensearch") #3235
• PR kiwix/defaults/main.yml: New kiwix-tools version 3.3.0-1 #3344

[holta]

Further testing will be very useful to confirm across all sorts of scenarios in coming days.

Thanks all who can help.

Also after kiwix-tools 3.3.1 is released in a few short days:

• https://github.com/kiwix/kiwix-tools/milestone/3

[holta]

Thanks to @deldesir who tested this on Debian 11 (Bullseye) on an x86_64 VM (with graphical desktop).

[deldesir]

Works perfectly on Ubuntu 22.10 and Debian 11.

[holta]

Many Thanks @deldesir:

1. I've cleaned up the upgrade path, to move /opt/iiab/kiwix/bin aside (if it already exists)
2. Further tested on "Raspberry Pi OS with desktop"
3. Inline docs much improved
4. Good Enough!

[holta]

Very useful kiwix-serve pre-doc, thanks to Renaud Gaudin:

• Create Kiwix-serve (API) documentation kiwix/kiwix-tools#498 (comment)