Enable optional ctx cb mode

[b0xcat]

Description

Saves around ~100kb of ram that would otherwise be used for the framebuffer. It does seem to have around a ~30% performance impact fps wise

Did some quick testing:

Memory use (Free bytes)

Measured after init by doing esp32.idf_heap_info(esp32.HEAP_DATA)

Region 1 is PSRAM

Region	FB+PSRAM	FB+Internal	CB+PSRAM	CB+Internal
0	32,031	8,859	32,031	32,031
1	1,668,016	1,732,920	1,768,356	1,783,716
2	12,488	4	12,504	1,244
3	21,572	4	21,572	17,472
4	7,672	4	7,672	7,672
Total	1,741,779	1,741,791	1,842,135	1,842,135