fix(hierarchicalGrid): Fix scrollbar not updated when data for children is loaded after initial load.

[skrustev]

Closes #4209

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code
• This PR includes API docs for newly added methods/properties
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes
• This PR includes behavioral changes and the feature specification has been updated with them

[skrustev]

There is another scenario that is not covered.
If there is no scrollbar initially , it is not shown after a row is expanded even though the grid can be scrolled.

Steps:

1. Add paging to the root grid and set perPage to 10 or set big height so there is no scrollbar initially.
2. Expand a row that fills the page and makes the grid scrollable.