1. add libphy.a librtc.a, but store in bt submodule, if someone use them, please copy to esp32/lib/ instead the origin one
2. add 07_blufi demo
3. change esp32/Kconfig to allow bt/wifi coexist
This change removes implicit WiFi/BT initialization from startup code.
"main" task is started once essential part of startup code is complete.
This task calls application-provided "int main(void)" function, which can call WiFi/BT init functions if necessary.
Note that with WiFi stack enabled, system_init will reset frequency to 240MHz.
To make this setting useful, esp32-wifi-libs submodule needs to be updated.
