refactor(ngrokapi): Refactor ngrokapi package to better support mocking

[jonstacks]

What

Step 1 in beefing up our test coverage. Rather than returning clients for everything, return interfaces that behave like the actual clients. This will allow us to rely on the interfaces in the rest of the code and eventually substitute mock clients so we can test the behavior of our controllers better.

How

Make interfaces for our clients and replace the actual implementation with the interfaces.

Breaking Changes

No

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 34 lines in your changes missing coverage. Please review.

Project coverage is 23.67%. Comparing base (382afff) to head (8099c2d).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/ngrokapi/edge_modules_https_clientset.go	0.00%	14 Missing ⚠️
internal/ngrokapi/clientset.go	0.00%	11 Missing ⚠️
internal/ngrokapi/edge_modules_tls_clientset.go	0.00%	5 Missing ⚠️
internal/ngrokapi/edge_modules_tcp_clientset.go	0.00%	3 Missing ⚠️
...nternal/controller/ingress/httpsedge_controller.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #578   +/-   ##
=======================================
  Coverage   23.67%   23.67%           
=======================================
  Files          88       88           
  Lines       12484    12484           
=======================================
  Hits         2955     2955           
  Misses       9339     9339           
  Partials      190      190           

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