Simple flash read command is not supported if Secure DL mode is enabled on the target.
Remove reference of this from the relevant docs part.
Related: https://github.com/espressif/esptool/issues/810
Related: ESPTOOL-567
Closes IDF-6468
List down considerations for the following areas:
- Hardware security
- Network security
- Product security
Also added brief explanation about "Security Policy" for ESP-IDF.
Closes IDF-1565