Don’t pass font to pain functions

[khaledhosny]

Avoids the hb_(font|face)_(reference|destroy) at each function call. If the user needs the font, they can pass the Python Font in the paint_state.

[khaledhosny]

Painting U+270D from tests/data/noto_handwriting-cff2_colr_1.otf 100000 times using paint functions that does nothing:

Without this change:

real    0m1.441s
user    0m1.423s
sys     0m0.013s

With this change

real    0m1.269s
user    0m1.252s
sys     0m0.012s

[behdad]

I was very worried before you said 100000 times :))

[khaledhosny]

I was very worried before you said 100000 times :))

:) I thought someone would be

[behdad]

LGTM.

[HinTak]

I was more worried about the mention of "pain" functions in the title. So harfbuzz is in the business of adding pain and suffering to the world now? 😉