[#1755] Fix Polymorphism errors look strange in LSP

Motivation and Context

Problem

The error pretty-printers/formatter we different in case of json & dev. This causes difference in printed error messages between CLI & LSP diagnostics

Solution

Unify/Extract the common bits between the different pp functions, in order to have the same error message in CLI & LSP

Description

Fixes #1755 (closed)

Component

• compiler
• website
• webide
• vscode-plugin
• debugger

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement (non-breaking change that improves performance)
• None (change with no changelog)

Changelog

Fixes the difference in error messages between CLI & LSP dianostics. Now the type error messages will be consistent across CLI & LSP.

Checklist:

• Changes follow the existing coding style (use dune @fmt to check).
• Tests for the changes have been added (for bug fixes / feature).
• Documentation has been updated.
• Changelog description has been added (if appropriate).
• Start titles under ## Changelog section with #### (if appropriate).
• There is no image or uploaded file in changelog
• Examples in changed behaviour have been added to the changelog (for breaking change / feature).