I'd recommend the 16f57 for this purpose.
this is a small microcontroller.
you just connect the LEDs 1:1 in that case,
no special circuit design.
but no one can know the equipment that is available to you.
or if you have access to materials like $1 prototype boards on the market.
such a flashlight that you describe could be made for about $5, powered by USB, including almost everything.
I reply because eventually i want to make a 16f57 LED matrix PCB, which also could be used to control a flashlight as well.
It seems to be a popular circuit.
when I was younger i've purchased some flashlight kits, based on the CD4017.
but that's not a microcontroller.
they suffered from static problems back then, I remember, because I had more than one of these kits.
might have been stuff manufactured in the early 1980s, and back then, horribly expensive.