Add Extract Variables with JavaScript in Synthetic Tests Multiple Step API

[maykungth]

What resources or data sources are affected?

datadog_synthetics_test

Feature Request

I request to support feature "extract variables from javascript" in Synthetic test (multiple step API).
Since sometimes we need to add conditions or modify the variables before setting them for next steps.

At this time, extract variable feature support types (grpc_message, grpc_metadata, http_body, http_header, http_status_code.) There is no javascript type.
https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/synthetics_test#nested-schema-for-api_stepextracted_value

References

No response