Remove char* array backed mem placeholders with magic size constants

The engine has tons of stuff like:
`uint8_t amtMemBuffer[512];`

This is very volatile and tedious to maintain. The magic number should either be replaced with sizeof() of object it gets size from or reworked to not have mem placeholders at all.

Start by searching the engine for char* or uint8_t arrays using fixed sizes such as amtMemBuffer[512]. Review each placeholder's allocation and the object or buffer size it represents before deciding whether sizeof() is applicable or the placeholder can be removed. Done means the targeted magic-size placeholders are replaced or eliminated without changing engine behavior.

Written by the indexing model from the issue text.