Find replacement for CONFIG_MBEDTLS_ALLOW_UNSUPPORTED_CRITICAL_EXT (IDFGH-11195)

[torkleyy]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

This flag is currently without any effect, as it has been removed upstream (see Mbed-TLS/mbedtls#4477).

This feature is crucial as major vendors of certificates use such unsupported extensions (see Mbed-TLS/mbedtls#2605).

I think there are two options to replace this functionality:

1. Replicate this functionality by implementing the callback (mbedtls_x509_crt_parse_der_with_ext_cb) and ignore unknown extensions (this is deemed insecure by mbedtls maintainers)
2. Allow the user to service such a callback

[mahavirj]

Thanks for notifying. We will remove this config from ESP32 mbedtls port. However, the alternative solution for this must be discussed in the upstream community itself. One of the suggestion can be found here: Mbed-TLS/mbedtls#3564 (comment)

[mahavirj]

Fixed with 0c3ed4f