[PATCH RESEND v3] Simple HiDPI support for GRUB2

[Zhang Boyang]

Hi,

This is a resend of my [PATCH v3].

Thank you.

Best Regards,
Zhang Boyang 

===

Changes in [PATCH RESEND V3]:
Rebased to latest git head.

Changes in [PATCH V3]:
1/2: To avoid interger overflow during scaling, this patch intruduces 
GRUB_FONT_MAX_DIMENSION and GRUB_FONT_MAX_SCALE. The font loader will now 
reject bad fonts and glyphs.
2/2: Make behavior configurable through a new environment variable 
'gfxterm_scale'.
Link: https://lists.gnu.org/archive/html/grub-devel/2022-06/msg00000.html

Changes in [PATCH V2]:
Now caches scaled bitmaps in each corresponding glyph. So it can be reused if 
same glyph is used many times.
Link: https://lists.gnu.org/archive/html/grub-devel/2022-05/msg00241.html

[PATCH V1]:
Link: https://lists.gnu.org/archive/html/grub-devel/2022-05/msg00232.html