Clarify that MALLOC_CAP_DEFAULT describes a memory capability
rather than the malloc() placement policy, so PSRAM-backed
capability allocations are documented correctly when malloc()
remains internal-only by default.
Closes https://github.com/espressif/esp-idf/issues/18391
Made-with: Cursor
The implicit promise of heap_alloc_caps() and friends is that the memory it
returns is fit for the purpose as requested in the caps field. Before
this commit, that did not happen; e.g. DMA-capable memory wass returned
from a correct region, but not aligned/sized to something the DMA subsystem
can handle.
This commit adds an API to the esp_mm component that is then used by the
heap component to adjust allocation alignment, caps and size dependent on
the hardware requirement of the requested allocation caps.
