Truncate large response body in legacy sandbox

[appurva21]

Issue

When setting up the legacy sandbox, the response buffer is, by default, converted to a string to support the global variable responseBody. This negatively affects the script execution performance for consumers who are not even consuming this value.

Fix

The ideal fix for this would be to lazily initialize responseBody through a getter, but due to how Uniscope is implemented, it is not possible to achieve that without a significant refactoring there (TLDR; the getter would get called at multiple places inside Uniscope).

The second best approach is to truncate the responseBody if it is too large (50MB). Since this is a deprecated syntax, users can (and should) use pm.response.text() for their requirements.