fix: merge existing baseEnvironment data and dataPropertyOrder on import

[PhilKes]

Fixes #6785

Currently when importing e.g. an OpenAPI YAML, the baseEnvironment is not updated correctly. Its data is overwritten (not merged with the existing data, which is very annoying) and the dataPropertyOrder is not updated correctly therefore leading to the issue described in #6785.

This PR:

• Merges the existing baseEnvironment.data with baseEnvironmentFromResources.data on import
• Correctly updates the baseEnvironment.dataPropertyOrder on import

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