Migrate from mocha + nyc to jest

[blitz-1306]

Preface

Some time ago I noticed that updating dependencies causing unexpected coverage drops. While digging, I discovered that it was happening after updating TypeScript to latest and caused by nyc not being updated for a while. As nyc does not seem to be maintained for a while, I decided to create PR to move out tests to jest.

Note

Benefits:

• Supports parallel test executon.
• Supports coverage (based on same logic as nyc, but only limited and supported subset).
• Supports tests filtering and.
• Clear docs: configuration, CLI options.

Changes

• Removed mocha and nyc dependencies alongside with related config files.
• Introduced jest and adapted test suites.
• Updated TypeScript to latest (with some other development dependencies).

Warning

Files in src/bin are no longer covered. Same happends with other coverage engines, like c8.

Regards.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (36ee1b0) 91.60% compared to head (5496a0e) 91.10%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #248      +/-   ##
==========================================
- Coverage   91.60%   91.10%   -0.51%     
==========================================
  Files         270      269       -1     
  Lines        6634     6461     -173     
  Branches     1350     1308      -42     
==========================================
- Hits         6077     5886     -191     
- Misses        291      468     +177     
+ Partials      266      107     -159     

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