Merge branch 'feature/update_at_bin' into 'master'

feat: Updated at bin to v1.7.6.0

See merge request sdk/ESP8266_NONOS_SDK!319

Merge branch 'feature/update_at_bin' into 'release/v3.0.5'

feat: Update at bin to 1.7.5

See merge request sdk/ESP8266_NONOS_SDK!296

# Feature

- Update to SDK version 3.0.4 and AT version 1.7.4.0
- feat(pp): Used beacon interval to calibrate timer to improve accuracy
- feat(net80211): Allowed ESP8266 to connect to AP without basic rate
- feat(system): revise flash map automatically when the firmware and flash map do not match.
- feat(at): Add at_nano demo to support 1MB flash
 
# Bug Fix
- fix(net80211): Fixed some connection failure issue during 11b with only AP mode
- fix(net80211): Fixed the memory leak problem when ESP8266 acts as AP and station is sending illegal messages
- fix(system): Fixed probable loss of system parameter if power down when erasing or writing the flash 
- fix(lwip): Fixed crash issue when SNTP is stopped
- fix(at): Fixed potential low risk of scan failure using the AT command to scan specified SSID

Merge branch 'feature/update_at_bin' into 'master'

feat: Update at bin to 1.7.4.0

See merge request sdk/ESP8266_NONOS_SDK!283

Merge branch 'feature/update_bin' into 'master'

feat: Update at bin on the latest branch

See merge request sdk/ESP8266_NONOS_SDK!271

Merge branch 'feature/update_bin' into 'master'

feat: Update at firmware bin

See merge request sdk/ESP8266_NONOS_SDK!264

Merge branch 'feature/update_version' into 'release/v3.0.0'

feat: Update at bin v1.7.1

See merge request sdk/ESP8266_NONOS_SDK!217

Merge branch 'feature/update_at_bin' into 'master'

feat: Update AT bin version 1.7.0

See merge request sdk/ESP8266_NONOS_SDK!47

feat(at): Update AT bin version 1.6.2

internal gitlab: d589238f

feat(bin): Update AT bin for SDK 2.2.0

internal gitlab: 0fecfc34