Improve exceptions to ClearMountsJob

[parition] Do not unmount /dev/mapper/ventoy

Re-organize Python implementations and fix memory issues

Ventoy uses /dev/mapper/ventoy to provide the ISO.
Unmounting /dev/mapper/ventoy is not desired since certain ISOs may have mounts that rely on it existing for the unpackfs step

Save obfuscated luks passphrase in calamares globals variables

Lock the description variable properly, so that while
it is being accessed from another thread (to read the
string for progress reporting) it doesn't get corrupted
by updates from the Python thread.

- run a target command
- emit lots and lots of progress signals

Unrelated, destructor = default is simpler than empty.

Python code that would run with Boost::Python, calling
target_env_call() with a single string parameter, would
fail in pybind11. Add the missing overload.

The logging functions and some other trivia can be
implemented the same way regardless of the backing
Python implementation.

The implementations can call the generic code
for wrangling QVariant into Python types.

This is code duplicated between the two implementation
directories (to be taken out shortly). It isn't generic
in a template-sense, but it does use the types and
support functions defined in the implementation-specific
PythonTypes header.

- pybind11 stuff in pybind11/ rather than python/
- Boost::Python stuff in pyboost/ rather than in libcalamares/

Adapt consumers, too (which are few).

Provide type aliases for more types, and a factory
function for None, in both implementations.

i18n: [calamares] Fix Ukrainian localization