[Feature] Timezone picking screen

[PedroHLC]

A new screen is required to select the new computer timezone (/etc/localtime), for that one may query the directory /usr/share/timezone recursively, listing only TZif2 files.

The user has to be able to select one and only one timezone from the list, a RadioButton in a ListView is recommended to achieve that.

It's not necessary to create a symlink in /etc/localtime as that will be appended to the setup script so the user can review it on later steps. So only saving which file was chosen is enough.

For layout/design inspirations, one can consult other screens like KeyboardPicker and LocaleSelect.

Estimated complexity: 100 lines of C code + 100 lines of QML.

Files that may be created:

• src/lib/timezone.hpp
• src/lib/timezone.cpp
• qml/TimePicker.qml

Files that have to be modified:

• src/main.cpp: Add include, instantiate new class, connect to a QML property.
• qml/MainContainer.qml: Needs to instantiate the new component and assign an id to it.
• chaotic-installer.pro Add new cpp and hpp to the build system.