feat: process lines related to metadata entity only

[scolladon]

Explain your changes

---

Check if a line is processeable as a metadata candidat before processing it.
Check is implemented at the base class level (StandardHandler.js) and declined when needed for specific use cases (InFolder metadata, InResource metadata and WaveMetadata specificities)

Local functional test, e2e test and perf test are passing

Does this close any currently open issues?

---

closes #548

• Jest test added to check the fix is applied.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (2e8f9fb) 100.00% compared to head (8cd9f05) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #554   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           31        31           
  Lines          850       863   +13     
=========================================
+ Hits           850       863   +13     

Impacted Files	Coverage Δ
src/service/inFolderHandler.js	100.00% <100.00%> (ø)
src/service/inResourceHandler.js	100.00% <100.00%> (ø)
src/service/standardHandler.js	100.00% <100.00%> (ø)
src/service/waveHandler.js	100.00% <100.00%> (ø)
src/utils/fsHelper.js	100.00% <100.00%> (ø)
src/utils/gitConstants.js	100.00% <100.00%> (ø)

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[codeclimate]

Code Climate has analyzed commit 8cd9f05 and detected 0 issues on this pull request.

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[github-actions]

Shipped in release v5.17.0.
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