fix(plugin-coverage): merge multiple results for a file

[Tlacenka]

Closes #560
Fixes part of #647

In this PR, I implement a merging logic in order to collect coverage for the same file system from multiple test suites:

• In case different coverage runs identify different branches of code/functions, all that are identified by any tool are registered.
• The hits of functions, branches and lines are merged. As long as a function, branch or line is covered by at least one test suite, it is considered covered.

Tested on our CLI + unit tested.

[nx-cloud]

☁️ Nx Cloud Report

CI is running/has finished running commands for commit 1eecaae. As they complete they will appear below. Click to see the status, the terminal output, and the build insights.

📂 See all runs for this CI Pipeline Execution

---

✅ Successfully ran 6 targets

• nx release --yes --dry-run
• nx affected:e2e --parallel=3
• nx affected -t unit-test --parallel=3 --coverage.enabled
• nx affected -t integration-test --parallel=3 --coverage.enabled
• nx affected:build --parallel=3
• nx affected:lint --parallel=3

---

Sent with 💌 from NxCloud.

[github-actions]

Code PushUp

🤨 Code PushUp report has both improvements and regressions – compared target commit 78ea50b with source commit 37b3283.

🏷️ Categories

🏷️ Category	⭐ Current score	⭐ Previous score	🔄 Score change
Code coverage	🟡 80	🟡 70
Performance	🟢 93	🟡 86
Accessibility	🟢 98	🟢 100
Best Practices	🟢 100	🟢 100	–
SEO	🟡 86	🟡 86	–
PWA	🟡 63	🟡 63	–
Bug prevention	🟢 100	🟢 100	–
Code style	🟢 99	🟢 99	–
Security	🟢 95	🟢 95	–
Updates	🟢 93	🟢 93	–
Custom checks	🟡 67	🟡 67	–

🗃️ Groups

👍 2 groups improved, 👎 1 group regressed

🔌 Plugin	🗃️ Group	⭐ Current score	⭐ Previous score	🔄 Score change
Code coverage	Code coverage metrics	🟡 80	🟡 70
Lighthouse	Performance	🟢 93	🟡 86
Lighthouse	Accessibility	🟢 98	🟢 100

18 other groups are unchanged.

🛡️ Audits

👍 9 audits improved, 👎 1 audit regressed, 11 audits changed without impacting score

🔌 Plugin	🛡️ Audit	📏 Current value	📏 Previous value	🔄 Value change
Lighthouse	Largest Contentful Paint element	🟩 2,040 ms	🟥 2,750 ms
Lighthouse	Background and foreground colors have a sufficient contrast ratio	🟥 0	🟩 0
Code coverage	Line coverage	🟩 91 %	🟨 66 %
Lighthouse	Max Potential First Input Delay	🟥 260 ms	🟥 370 ms
Lighthouse	Largest Contentful Paint	🟩 2.0 s	🟨 2.7 s
Code coverage	Function coverage	🟨 76 %	🟨 64 %
Lighthouse	Total Blocking Time	🟩 120 ms	🟨 230 ms
Code coverage	Branch coverage	🟨 83 %	🟨 82 %
Lighthouse	Time to Interactive	🟩 2.6 s	🟩 2.7 s
Lighthouse	Cumulative Layout Shift	🟨 0.147	🟨 0.148
Lighthouse	Minimizes main-thread work	🟥 2.5 s	🟥 3.1 s
Lighthouse	Avoids enormous network payloads	🟩 Total size was 432 KiB	🟩 Total size was 432 KiB
Lighthouse	Speed Index	🟩 1.6 s	🟩 1.5 s
Lighthouse	Uses efficient cache policy on static assets	🟨 11 resources found	🟨 11 resources found
Lighthouse	First Meaningful Paint	🟩 1.1 s	🟩 1.3 s
Lighthouse	Metrics	🟩 2600	🟩 2671
Lighthouse	First Contentful Paint	🟩 1.1 s	🟩 1.1 s
Lighthouse	JavaScript execution time	🟩 0.1 s	🟩 0.1 s
Lighthouse	Initial server response time was short	🟩 Root document took 0 ms	🟩 Root document took 10 ms
Lighthouse	Network Round Trip Times	🟩 10 ms	🟩 0 ms
Lighthouse	Server Backend Latencies	🟩 10 ms	🟩 10 ms

501 other audits are unchanged.

[BioPhoton]

LGTM

[matejchalk]

Great effort 👍