refactor(app): Remove notification event emitters

[mjhuff]

Partially closes RAUT-990

Overview

Event emitters don't provide anything that a callback doesn't. In fact, they make things worse by:

1. Making testing much more difficult. Mocking event emitters isn't fun.
2. There are all sorts of emitter leak issues that can arise.
3. The console gets spammed with warning messages.

Let's use callbacks from the IPCRenderer -> app without the unnecessary event emitter intermediary. Let's also move some of the types involving the data received from the shell layer to the proper place.

Test Plan

• Smoke tested the app, making sure notifications work.

Risk assessment

low

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (9dc8f2d) 67.74% compared to head (f3a2bb3) 67.76%.
Report is 5 commits behind head on chore_release-7.2.0.

Additional details and impacted files

@@                   Coverage Diff                   @@
##           chore_release-7.2.0   #14504      +/-   ##
=======================================================
+ Coverage                67.74%   67.76%   +0.02%     
=======================================================
  Files                     2517     2517              
  Lines                    72068    72055      -13     
  Branches                  9278     9276       -2     
=======================================================
+ Hits                     48823    48829       +6     
+ Misses                   21027    21008      -19     
  Partials                  2218     2218              

Flag	Coverage Δ
app	64.63% <50.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
app/src/resources/useNotifyService.ts	84.61% <100.00%> (+48.90%)	⬆️
app/src/redux/shell/remote.ts	0.00% <0.00%> (ø)

... and 10 files with indirect coverage changes

[sfoster1]

We love to see it. Though maybe make those test changes that are easier?