translate tests to new testing framework

[haberdashPI]

This is a complete overhaul of the CI/testing setup for this project. It makes a few small changes to the project as well:

1. Fix various bugs that were missed when merging Breaking Changes for 0.4 #70: these were missed due to the flaky tests — which were the reason to revamp the tests here

2. Remove excessive UI features: there is some feature bloat in the config commands that was annoying to add tests for and did not really imporve the user experience, so I have simplified how master and user keybindings are activated.

[codecov]

Codecov Report

Attention: Patch coverage is 99.51456% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.54%. Comparing base (e61eaee) to head (4697aa8).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/extension/keybindings/index.ts	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #74      +/-   ##
==========================================
+ Coverage   78.67%   83.54%   +4.86%     
==========================================
  Files          25       27       +2     
  Lines        2420     7195    +4775     
  Branches      477      759     +282     
==========================================
+ Hits         1904     6011    +4107     
- Misses        324     1184     +860     
+ Partials      192        0     -192     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.