Changes:
KConfig: The option CONFIG_ESP32_RTCDATA_IN_FAST_MEM is added in Kconfig file for esp32 component.
esp32.common.ld: added support of RTC_DATA_ATTR, RTC_RODATA_ATTR data placement into appropriate segment according to Kconfig option.
esp32.ld: linker script is modified to set alias for memory segment selected by Kconfig option to place data. The segments for force placement are added for RTC_FAST_ATTR, RTC_SLOW_ATTR attributes.
esp_attr.h: added new attributes RTC_FAST_ATTR, RTC_SLOW_ATTR for force placement into fest/slow memory.
test_rtc_fast.c: Added unit test cases to check data placement into appropriate memory segment.
Updated documentation for RTC_DATA_ATTR, RTC_FAST_ATTR, RTC_SLOW_ATTR in deep_sleep_stub.rst file.
TW#18001
Closes https://github.com/espressif/esp-idf/issues/1553
KonstantinKondrashov