LibGfx: Replace FLATTEN with ALWAYS_INLINE for `draw_glyph()` overload

While IMO, the change makes sense on its own as flattening this function
will just duplicate the code from `draw_glyph()` with no benefits, this
is not what motivated this patch.

When compiling with debug information and ASAN, GCC 13.2 would issue
this warning:

Userland/Libraries/LibGfx/Painter.cpp: In member function ‘void Gfx::Pai
nter::draw_glyph(Gfx::FloatPoint, u32, Gfx::Color)’:
Userland/Libraries/LibGfx/Painter.cpp:1354:14: note: variable tracking s
ize limit exceeded with ‘-fvar-tracking-assignments’, retrying without
 1354 | FLATTEN void Painter::draw_glyph(FloatPoint point, u32 code_poin
t, Color color)
      |              ^~~~~~~

From what I've read online, this is caused by some limit on the number
of symbols in the compiler's internal data structures. People at Google
have fixed this warning by splitting functions:
https://codereview.chromium.org/1164893003

While getting us rid of the warning, it also drastically improves
compilation time. Going from 1min27 to 59s on my machine.

Userland/Libraries/LibGfx/Painter.cpp

@@ -1351,7 +1351,7 @@ void Painter::draw_scaled_bitmap(IntRect const& a_dst_rect, Gfx::Bitmap const& s
     }
 }
 
-FLATTEN void Painter::draw_glyph(FloatPoint point, u32 code_point, Color color)
+ALWAYS_INLINE void Painter::draw_glyph(FloatPoint point, u32 code_point, Color color)
 {
     draw_glyph(point, code_point, font(), color);
 }