Add more allocators

[richardbiely]

Currently, all allocations (save for chunks) are done using the global new operator and depend purely on the system.

Specific allocators are needed because:

• they give complete knowledge over allocations done by the library
  • we already can sort of do this via GAIA_PROF_ALLOC, GAIA_PROF_ALLOC2 but it only works with Tracy and we would need to profile the program from the start which is a bummer
• help manage memory better and help performance, also gives users to swap this for their own impementation (e.g. when used with some engine)