soc: esp32: unify runtime heap usage

This commit applies several changes in the way "heap_runtime"
feature is used. It can't be split due to bisectability issues.

Whenever the feature is enabled, a new heap is created and
custom malloc/calloc/free functions are added into the build
system. Those functions are currently used for internal Wi-Fi and BLE
drivers only.

Such changes are described below:

1) Rename heap.c to esp_heap_runtime.c for better readability.
2) Rename RUNTIME_HEAP to HEAP_RUNTIME to make it similar to what is
available in Zephyr.
3) Add runtime heap to BT as such as Wi-Fi.

Fixes #79490
Fixes #79470

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>