Fix for issues where RTC FAST memory is updated as part of going into deep
sleep. Very high risk if heaps are in RTC memory - in particular task stacks
may be in RTC memory, but also other variables.
Also fixes potential concurrency problems as RTC FAST memory is not accessible
by CPU during the CRC calculation itself.
Method:
- Disable interrupts (currently for single core only, will need update for S3)
- Load all registers before calculating CRC or going to sleep
Commit aa43ed8 was fixing the light sleep overhead calculation for
ESP32-S2. However it also changed the overhead values for ESP32,
resulting in incorrect light sleep time. This caused regression in
light sleep example test.
Revert the original values for the ESP32, keep different set of values
for each chip.
Based on the original code (`esp32/sleep_modes.c`), `RTC_SLEEP_PD_XTAL`
is always given as an argument to `esp_sleep_start`. Enforce this in
function to get power down flags to avoid redundancy.
