feat: apisix enable_encrypt_fields should support plugin fields that are deeply situated, array elements, etc.

[shreemaan-abhishek]

Description

Current Situation:

APISIX enable_encrypt_fields only supports sensitive fields situated within two levels of depth. ref:

apisix/apisix/plugin.lua

Line 1011 in cca94f1

-- we only support two levels

and it would not be possilbe to specify fields like kafka logger's brokers.sasl_config.password in any of the following ways even if fields from multiple depth levels were supported because brokers is of type array.

encrypt_fields = { "brokers.sasl_config.password" }
-- or
encrypt_fields = { "brokers.foreach.sasl_config.password" }
-- or
encrypt_fields = { "brokers.all.sasl_config.password" }
-- none of the above options work 🤷🏻‍♂️

Expected Situation:

There should be a mechanism to include plugin fields for encryption regardless of their nature. Due to this limitation it's not possible to include fields like kafka-logger's brokers.sasl_config.password, aws-lambda's secretKey.

This limitation was found during the implementation of #11095

[starsz]

Could we check the type of the plugin fields, if it's an array, then we encrypt the values in this array.