make the context timeout configurable when calling the schema registry

[fouadkada]

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Context

The context used in the processor_schema_registry_decode and processor_schema_registry_encode has a hardcoded timeout when calling the schema registry.

This is problematic when the schema registry does not respond within the 5 seconds hardcoded value.

This change introduces a read_timeout configurable string value that is parsed to a duration using time.ParseDuration to allow the user to customize the duration after which the context timeouts.