[BUG] _force_eager_loading depends on import/instantiation order

[wbrgss]

click for obligatory `pip list | grep dash`

package	version
dash	1.5.0
dash-auth	1.2.0
dash-bio	0.1.1
dash-bio-utils	0.0.2
dash-canvas	0.0.11
dash-core-components	1.4.0
dash-cytoscape	0.0.5
dash-dangerously-set-inner-html	0.0.2
dash-daq	0.1.0
dash-design-kit	1.3.0 /home/plotly/Workspace/dash-design-kit
dash-design-kit-docs	1.3.0
dash-enterprise-auth	0.0.2
dash-extra-components	0.0.1
dash-html-components	1.0.1
dash-renderer	1.2.0
dash-table	4.5.0

In dash v1.5.0, instantiating or importing an "app" (i.e. app = dash.Dash(__name__)) before importing a package with _force_eager_loading = True defined in its __init__.py file will still result in lazy loading. Expected behavior is that eager loading will be forced, as implied by the flag name. This can result in missing dependencies, e.g. plotly.js:

Confirmed as reproducible by @Marc-Andre-Rivet