Positron Assistant: Enable the "echo" provider for e2e testing

[jonvanausdeln]

It was mentioned that there is the start at least of an "echo" provider in Positron Assistant. Something that could act as stub for e2e testing.

I'd like to at least get the current functionality enabled in a way that it can be used for e2e testing.

[timtmok]

This has been added and can be set by adding "positron.assistant.testModels": true to the settings.json file.

It will enable AWS Bedrock, Echo, and Error test models. AWS Bedrock is a bit complicated to set up but does work by setting the environment variables for the AWS access keys before starting Positron. There currently isn't a way to configure it from the dialog.

[jonvanausdeln]

Enabled as of 2025.04.0-173. I'll open issues if there are future requests for features on the echo provider