HaikuDepot: Languages List

Abstacts the list of supported languages into
the LanguageModel class preventing use of
List. Also; fix a few cases where newer
logging techniques may have caused incorrect
logic flow.

Relates To #15534

Change-Id: I144fe4788abdaf0d93e53eeabc97b3f7aa2ec710
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3085
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Better Logging

Changes the logging in HD to use a macro for the
various log levels to declutter the code and to
make it easier to more systematically log.

Change-Id: I025970707a0a11e7e3aaa4b52fc91288af0183f5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3018
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Process and Data-loading Improvements

This change is a reshuffle of the backend processing involved in the
aquisition of data from servers including the pull-down and load of
HPKR data as well as the pull-down and load of data from the
HaikuDepotServer (HDS) system. The driver for this change is to
implement an initial implementation of a progress bar for the
loading of data as the application starts.

The following are notable changes;

* Removed some previously attempted 'functional style' logic in the
model which didn't fit well with C++
* Use of the base-url in the logical mapping from HDS and HD data is no
longer required and has been removed
* Some logging has been improved making it clearer which part of HD
is producing the logging which in turn helps with debugging issues
* List class has been modified to more cleanly support sorted lists
and binary searches; tests have also be updated accordingly
* Reorganise and tidy-up of the data-loading processes' structures
* The local repository update (HPKR) and data-load occur in background
processes now in the same system as the HDS data-load - this has been
crudely shifted from the MainWindow to new Processes and incorporated
into the background processing system
* The 'state-machine' background process runner is now replaced with a
'coordinator' style approach that can more easily handle the new
processes related to HPKR loading.
* Progress for loading processes is shown in the main window in the
WorkStatusView - this is flickering a bit, but basically works
* Added some documentation regarding how Processes work in the system
* The "Refresh Repositories" menu item now also updates data from HDS
* The "Refresh Repositories" menu item is disabled when the background
processes are running that update the repository data

Some further refinement would be good, but this change is large enough
for one round of improvements. There is an issue that the status bar
is used for screenshot display as well as this data-loading, but that
was the case before so it is something that can be dealt with later if
it is a problem.

Change-Id: I7668307645e3aabaf7e4a6e37e2cca80cc0f489e
Reviewed-on: https://review.haiku-os.org/770
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

HaikuDepot : Streaming Icon Meta-Data Parser

More background work for later performance improvements.
This change generalizes the parsing of meta-data from
JSON streams as similarly structured meta-data is
anticipated to be carried in other payloads. Unit tests
have also been implemented to provide coverage on this
new functionality.