H2T (Host-to-target) installs and prevent host pollution

[h8d13]

This is a follow up to my last PR#3928 and original ISSUE#3599

What we achieve with such a patch:

• Prevent polluting the host by having a hacky running_from_host definition
  • Skip set_kb_layout (will be set on target only) via installer.set_keyboard_language() and set_vconsole()
• This is added to main __init__.py to print: EXAMPLE:

Fetching Arch Linux package database...
Checking version...
Running from host (H2T Mode)...

Or Running from ISO (Live Mode)

And will be present in logs to have a trace too (useful if outdated system deps or straight up missing deps).

End result: Makes it so that if you are installing say from a US layout computer and target uses a different layout (ex: laptop), we do not modify the host system and can be built-upon for other host-checks if needed (say for example: extra deps checks or other host isolation related needs).

• Readme clarification Host to target installs without an ISO!
• Pyright type annotations fixes (was giving me errors but can revert it if needed)