Added support basic settings form of custom widgets

[kalutkaz]

Pull Request description

In the current version of Thingsboard users can't create custom basic settings components, as BasicWidgetConfigComponent isn't shared and registration of basic settings forms doesn't work properly (basic components put into advanced components map as a result system doesn't see basic forms).

This PR share BasicWidgetConfigComponent and update registerWidgetSettingsForms to allow the creation of custom basic settings forms.

General checklist

• You have reviewed the guidelines document.
• Labels that classify your pull request have been added.
• The milestone is specified and corresponds to fix version.
• Description references specific issue.
• Description contains human-readable scope of changes.
• Description contains brief notes about what needs to be added to the documentation.
• No merge conflicts, commented blocks of code, code formatting issues.
• Changes are backward compatible or upgrade script is provided.
• Similar PR is opened for PE version to simplify merge. Crosslinks between PRs added. Required for internal contributors only.

Front-End feature checklist

• Screenshots with affected component(s) are added. The best option is to provide 2 screens: before and after changes;
• If you change the widget or other API, ensure it is backward-compatible or upgrade script is present.
• Ensure new API is documented here