fix(hgrid): Expose onGridInitialized output #6860

[dkamburov]

Closes #6860

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 (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• 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 (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them

[MayaKirova]

@dkamburov
It seems that the additional change detection fully initializes the child grid before triggering the onGridCreated event so now if you try to subscribe to an initialization event like the onColumnInit:
event.grid.onColumnInit.subscribe(x => console.log('emitted'));
It will never fire.

[MayaKirova]

@dkamburov You could force the child grid to register in its API service instead of calling detect changes, for example:

    this.hGrid._setupServices();
    this.layout.onGridCreated.emit({
        owner: this.layout,
        parentID: this.rowData.rowID,
        grid: this.hGrid
    });

This should ensure the grid registered before the event is emitted.

done