Invalid encoding for non-ascii JSON/HAR

[stek29]

Description:
Strings exported in JSON/HAR are invalid if request/response isn't ASCII but UTF-8.
And if Request/Response is not a valid string at all -- and is a binary data -- export is wrong too.

Steps To Reproduce:

• Make a request/response containing non-ascii characters
• Export as JSON or as HAR
• Open exported file as UTF-8 file

Expected behavior:
Strings are correctly exported

Actual behavior:
Strings are broken and aren't in UTF-8 format

Version:
3.20.1