renderer: add --no-fade-in

[alba4k]

This PR implements what I wished for in #452

It simply adds a --no-fade-in flag that disables the fade in animation when used, overwriting the use of no_fade_in (as if it was always set to true).

For the implementation, I mainly looked at the way --immediate-render was implemented.

LMK if there are any changes I should make, the main doubts I have are:

• is the internal m_bNoFafeIn name correct? not sure what the m and the b stand for.
• the commit name, should it start with renderer:? Would something else like core: be better?