Changed the kafka_types.go file and introduced a mapvalue struct.

[TheJadeLion2004]

In kvs.go, introduced an InsertValueMap function and a SecretProvider interface.

What this PR does / why we need it:

The PR attempts to change the type of the Kafka struct from a dictionary of strings to a dictionary of variant type, where the variant contains either a string or a *plugins.Secret. Needed to also change the InsertStringValueMap function and replace it by an insert MapValueMap function which does whatever the original function does, but now, tries to add elements to the map of the variant type.

An interface was used to avoid circular dependency, however there is some deepcopy error that is being generated.

Which issue(s) this PR fixes:

Fixes # #1152

Does this PR introduced a user-facing change?

Additional documentation, usage docs, etc.:

[TheJadeLion2004]

I've created a pull request in order to check the base logic, and to get help in verifying errors. This is NOT a working PR.