Add tests for `gfx_SetDraw`

[ZERICO2005]

Add tests for uint8_t gfx_GetDraw

If you need help or clarification on how gfx_GetDraw works, you can ping one of the developers in https://discord.gg/5yVK3UjcX7 or ask a question in this github issue.

TODO:

• test the return value of gfx_GetDraw after gfx_Begin
• make sure the value from gfx_GetDraw matches the value passed in from gfx_SetDraw
• test gfx_GetDraw after calling gfx_SwapDraw