Now that the supported CMake version is >=3.16, this code can be
simplified.
The code to deduplicate the directories can be removed since this is
handled by target_link_directories.
Fix dependency tree so that lwip doesn't depend on any specific network
interface component.
Network interface drivers shall depend on esp_netif.
esp_netif shall depend on lwip (but not on any specific interface
driver) -- it optionally depends on vfs and esp_eth (need ethernet
header for L2/bridge mode)
Some components were including esp_timer.h without declaring a
dependency on esp_timer component. This used to work due to a
transitive public dependency on esp_timer from freertos component.
Add explicit dependencies where needed.
Also some source files were using esp_timer functions without
including the header file. This used to work because esp_timer.h was
included from freertos port header file. This commit adds esp_timer.h
includes where needed.
Moved the following kconfig options out of the target component:
* ESP32_X_BROWNOUT_* -> esp_system
* ESP32_X_DEBUG_OCDAWARE -> esp_system
* APP_NO_BLOBS -> build type (main kconfig)
* add esp-phy-lib submodule
* move libphy.a and phy_init.c from esp_wifi to esp_phy
* move librtc.a from esp_wifi to esp_phy
* move libbtbb.a from bt to esp_phy
* corresponding updates to build system
