fix: update binding_to_syntax to use singleton scope according to docs

[notaphplover]

Description

This PR adds singleton scope to those bindings which are singletons according to docs.

See https://github.com/inversify/InversifyJS/blob/master/wiki/scope.md#bindings-that-will-inject-an-object for more information

Related Issue

#1297

Motivation and Context

According to docs, the following bindings should be in singleton scope:

• toConstructor.
• toFactory.
• toFunction.
• toAutoFactory.
• toProvider.

Actually, those bindings have the transient scope

How Has This Been Tested?

I've added a test for each type of binding to ensure onActivation is called once

Types of changes

• Updated docs / Refactor code / Added a tests case (non-breaking change)
• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the changelog.

[PodaruDragos]

LGTM

[dcavanagh]

LGTM