Create dedicated function for `xPortGetFreeHeapSize()` that only reports on DRAM.

Update and export `umm_free_heap_size()` to report the free Heap space of the current Heap. Updated ESP.getFreeHeap() to use.

Replace internal function `umm_free_heap_size_lw()` with `umm_free_heap_size()`.

See umm_malloc/Notes.h entry Sep 26, 2022 for more specifics.

uncrustified `umm_poison.c`

While touching and regression testing of build macros for umm_info...
and umm_stats..., improved/fixed macros for better support of
build options specified through Sketch.ino.globals.h.

Improve empty function situation around build option UMM_INFO.