Added lwIP hooks which could be optionally overwritten in the
application code. These three options are provided in Kconfig:
* NONE: No hook support
* DEFAULT: Default implementation is provided. If IDF doesn't
have a specific hook implementation, an empty stub is provided, which
could be overwritten by strong implementation in application code.
* CUSTOM: Hooks are declared only to be implemented in application code.
Merges https://github.com/espressif/esp-idf/pull/6034
