Introduce the experimental Ethernet sublayer (parent/child VLAN, optional
switch path, iodriver provider), restructure eth test apps, and document
the new APIs.
Fixed memory leak in emac_esp_new_dma function.
Polished ESP EMAC cache management.
Added emac_periph definitions based on SoC features and improved(generalized) ESP EMAC GPIO
initialization.
Added ESP EMAC GPIO reservation.
Added check for frame error condition indicated by EMAC DMA and created a target test.