Replace NetworkManagerProvider and leave one single provider on App

[enemycnt]

Description

Related Issue Or Context

Closes: #222

How Has This Been Tested? Testing details.

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 change)
• Documentation

Checklist:

• I have commented my code, particularly in hard-to-understand areas.
• I have ensured that all acceptance criteria (or expected behavior) from issue are met
• I have updated the documentation locally and in chainbridge-docs.
• I have added tests to cover my changes.
• I have ensured that all the checks are passing and green, I've signed the CLA bot

[render]

Your Render PR Server URL is https://chainbridge-pr-233.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-c9ca0kc41lsecbssflpg.

[lgtm-com]

This pull request introduces 16 alerts and fixes 6 when merging 4541768 into ac33bcb - view on LGTM.com

new alerts:

• 16 for Unused variable, import, function or class

fixed alerts:

• 6 for Unused variable, import, function or class

[lgtm-com]

This pull request introduces 16 alerts and fixes 6 when merging ef7017c into ac33bcb - view on LGTM.com

new alerts:

• 16 for Unused variable, import, function or class

fixed alerts:

• 6 for Unused variable, import, function or class