In situations where idle task runs a lot of idle hooks or cleanup code
(due to pthread local storage, etc) it can use more than 1KB of stack.
(I think the trigger is if a context switch happens at the right point
in the TLS cleanup).
Also removes an sdkconfig.default which accidentally set all config items,
including this stack size.
This commit removes the lookup table mode due to inferior performance when compared
to linear mode under attenuation 0, 1 and 2. However small portions of the lookup table
are kept for the higher voltages of atten 3 (above ADC reading 2880). That voltage range
in atten 3 has non linear characteristics making the LUT performan better than linear mode.
1. Support built-in ADC for I2S.
2. Modify code of ADC, made no change to the original APIs.
3. Add APIs in I2S:
esp_err_t i2s_set_adc_mode(adc_unit_t adc_unit, adc1_channel_t adc_channel);
4. Add I2S ADC/DAC example code.
5. add old-fashion definition to make it more compatible
6. replase spi_flash_ APIs with esp_partition_ APIs
7. add example of generating audio table from wav
8. change example sound
