ESP32 wifi should be able to use SPIRAM heap for buffer allocation

[Mierunski]

Is your enhancement proposal related to a problem? Please describe.
I'm currently migrating solution based on esp32 which used Zephyr 3.6.0
Issue is partly related to this: #78305

Previous behavior was that when SPIRAM was enabled, all memory allocations were moved to SPIRAM heap by default.
Now with shared multi heap its possible to allocate data on user side, but it does not work for libraries, especially espressif wifi driver, where packets are allocated internally, so switching CONFIG_ESP32_WIFI_NET_ALLOC_SPIRAM moves only initialization data, but buffer allocations are done in system heap.

This way, we are running out of memory, as we cannot pass option to use shared multi heap for network buffers internally in wifi driver

Describe the solution you'd like
KConfig option to enable allocation of network buffers in WIFI driver using SPIRAM heap.
Or option to allow previous behavior, where all malloc calls where forwarded to SPIRAM heap

This is critical for us, as with current implementation we are stuck on zephyr 3.6 because of this change

[rftafas]

First: moving network buffers to shared heap (i.e. to PSRAM) is a pending task internally. No release date set for it, though. I also suggest giving 4.1 a try, as there are a lot of fixes and improvements being missed.

Second: it is already possible to create buffers with the shared multi heap API and parts of Wi-Fi stack can be moved to PSRAM already. Mandatory readings:

• https://docs.zephyrproject.org/latest/kernel/memory_management/shared_multi_heap.html
• https://developer.espressif.com/blog/2024/12/zephyr-how-to-use-psram/
• WIP to move LVGL and MbedTLS buffers to PSRAM in soc:esp32: Add config allow MbedTLS heap and LVGL Frambuffer use SPI RAM #86049
• Similar restrictions as the ones on ESP-IDF apply: https://docs.espressif.com/projects/esp-idf/en/v5.2.5/esp32s3/api-guides/external-ram.html