Refactor JSI conversion

[msluszniak]

Description

Introduces a breaking change?

• Yes
• No

Type of change

• Bug fix (change which fixes an issue)
• New feature (change which adds functionality)
• Documentation update (improves or adds clarity to existing documentation)
• Other (chores, tests, code style improvements etc.)

Tested on

• iOS
• Android

Testing instructions

• Run tests and check that the results are the same
• Run all demo apps and check that there are no degradations in any functionality

Screenshots

Related issues

Closes #785

Checklist

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly (No changes in public API)
• My changes generate no new warnings

Additional notes

[mkopcins]

approved by mistake