EstNLTK analyzer

[osma]

This PR adds a new analyzer to support lemmatization using EstNLTK, a natural language analysis toolkit for the Estonian language.

Note that the indirect dependencies of EstNLTK are quite large, with around ~500MB of libraries.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.63%. Comparing base (d907024) to head (66f577d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #818   +/-   ##
=======================================
  Coverage   99.63%   99.63%           
=======================================
  Files          93       95    +2     
  Lines        7141     7170   +29     
=======================================
+ Hits         7115     7144   +29     
  Misses         26       26           

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🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[osma]

The test coverage is not 100%. I think that's due to how optional backends are handled in the initialization code, that I copied from the spaCy analyzer. The same problem is already there for spaCy, so I think it would make sense to fix that first in main, then apply the same solution in this PR.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[osma]

The initialization problem was fixed for spaCy in PR #820, already merged to main.
I rebased this PR branch and adapted it accordingly. I think all is now well.

This still needs wiki documentation, maybe also a mention in the Annif tutorial.

[osma]

I added a brief section about this analyzer on the wiki page for Analyzers.

I don't see any mention of specific analyzers in the Annif tutorial, so I don't think this needs to be mentioned there.

[juhoinkinen]

👍

[juhoinkinen]

I added an estnltk section to the Optional features page of wiki too (and updated the whole page to use poetry instead of pip for installing dependencies when using dev installation).