fonts: add per font sizing for themes

[KrahJohlito]

Pull Request checklist

Note: these are not necessarily requirements

• I reformatted the code with clang-format
• I checked to make sure my submission worked
• I am the author of submission or have permission from the original author
• Requires update of the PS2SDK or other dependencies
• Others (please specify below)

Pull Request description

This adds per font sizing for custom themes.. I wanted per element but might cause performance issues so I think this is a fair compromise.

• cfg entry example:

default_font=myDefaultFont.ttf
default_font_size=20

font1=myOtherFont.ttf
font1_size=12

main3:
 type=ItemsList
 font=0
main4:
 type=ItemText
 font=1

so in this example the games list has a font size of 20 using myDefaultFont.ttf and the game id uses a font size of 12 using myOtherFont.ttf.