Fix `unresolved` types in `get-scope`

Motivation and Context

There was an issue reported by serokell team that after ligo 0.51.0 there was a lot of unresolved types for definitions

The root cause of the problem was that the stdlib was not loaded in the typing context used by get-scope

Fixes #1514 (closed)

Description

This MR add stdlib in the type context used by get-scope & it also fixes an issue where type could not be resolved for mutable let bindings

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

For a file like

type user = {
  is_admin : bool,
};

const alice : user = {
  is_admin : true,
};

const alice_admin : bool = alice.i

Before fix

$ ligo.57 info get-scope y.jsligo --format dev --with-types
...
Variable definitions:
(alice#1 -> alice) 
...
Content: |unresolved|
...
(alice_admin#2 -> alice_admin) 
...
Content: |unresolved|
...
...

After fix

$ ligo info get-scope y.jsligo --format dev --with-types
...
Variable definitions:
(alice#1 -> alice) 
...
Content: |core: user|
...
(alice_admin#2 -> alice_admin) 
...
Content: |core: bool|
...
...

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).