Add --metric/-m option to eval command to select metric(s)

[osma]

This PR implements a new option -m/--metric for the annif eval command. It can be used (and repeated) to select the metric(s) to calculate, instead of all of them. Example:

annif eval my-project -m F1@5 -m NDCG /path/to/my-corpus

Fixes #545

This is useful for DVC as well to avoid introducing a lot of unnecessary metrics into experiments.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

Merging #558 (8da9e49) into master (49aa5df) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #558      +/-   ##
==========================================
+ Coverage   99.46%   99.50%   +0.03%     
==========================================
  Files          82       82              
  Lines        5428     5443      +15     
==========================================
+ Hits         5399     5416      +17     
+ Misses         29       27       -2     

Impacted Files	Coverage Δ
annif/cli.py	99.63% <100.00%> (+<0.01%)	⬆️
annif/eval.py	100.00% <100.00%> (ø)
tests/test_cli.py	100.00% <100.00%> (ø)
annif/backend/yake.py	98.23% <0.00%> (+1.76%)	⬆️

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