heap_caps_realloc() function

Reallocate memory previously allocated via heap_caps_malloc() or heap_caps_realloc(). Equivalent semantics to libc realloc(), for capability-aware memory. In IDF, ``realloc(p, s)`` is equivalent to ``heap_caps_realloc(p, s, MALLOC_CAP_8BIT)``. 'caps' parameter can be different to the capabilities that any original 'ptr' was allocated with. In this way, realloc can be used to "move" a buffer if necessary to ensure it meets a new set of capabilities.