Added check to whether nvs_keys partition is provided or not in partiton csv.
Converted nvs_sec_provider_register_flash_enc_ctr and nvs_sec_provider_register_hmac_ctr
functions from __attribute__(constructor) to ESP_SYSTEM_INIT_FN.
* All components which won't build (yet) on Linux are excluded.
This enables switching to Linux in an application without
explicitly setting COMPONENTS to main in the main
CMakeLists.txt.
* ESP Timer provides headers for Linux now
* automatically disabling LWIP in Kconfig if it is not available
doc(linux): brought section
"Component Linux/Mock Support Overview" up to date
