Inspection warning when disabling a nonexistent observer in events.xml

[DmitryFurs]

Is your feature request related to a problem? Please describe.

Version 3.0.0 inspection warning when disabling a nonexistent plugin in di.xml. It will be very useful to add the same behavior for observers.

Currently, when we disabling the nonexistent observer, we don't see any inspection notifications

Describe the solution you'd like (*)

Implement the same inspection warning for observers as for plugins.

Additional context

#147
#382

[m2-assistant]

Hi @DmitryFurs. Thank you for your report.
To help us process this issue please make sure that you provided sufficient information.

Please, add a comment to assign the issue: @magento I am working on this

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[drpayyne]

@magento I am working on this