[ECS] : console escapes backslash when configuring task definition via JSON

Whenever a user utilises the ECS Console to create a new task definition using the 'JSON' representation, the ECS console escapes “\” when entered in values of task definitions.
It is no longer possible to enter valid JSON values containing newlines into the ENV (\n) of a task definition via the console because the form fields are only single line text fields which don't support newlines. This has been an issue for many months.

Creating the task definition with new lines (\n) via the SDK or CLI is working (the backslash "\\" is not escaped).

Whenever I tried to introduce a new line within the 'Environment' portion, the console escapes the backslash, so as result, it converts a newline (\n) into (\\\n) escaping the backslash.

**Which service(s) is this request for?**
This could be Fargate, ECS

The issue names no repository files, tests, or implementation entry points. Start by reproducing the behavior in the ECS Console JSON task-definition editor with an Environment value containing \n, then verify that the submitted task definition preserves the intended newline escape as the done condition.

Written by the indexing model from the issue text.