[Android] Allow setting certain defines without modifying engine source

[rh101]

Describe your changes

Allow a game project to define the values of AX_ENABLE_CACHE_TEXTURE_DATA and AX_ENABLE_RESTART_APPLICATION_ON_CONTEXT_LOST without having to modify the engine source code.

For example, this may be done via cmake, prior to the include(AXBuildSet) line:

if(ANDROID)
    add_definitions(-DAX_ENABLE_CACHE_TEXTURE_DATA=0 -DAX_ENABLE_RESTART_APPLICATION_ON_CONTEXT_LOST=1)
endif()

Issue ticket number and link

#1211 (comment)

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