crypto/tss/eddsa: add some tests

[cychuang0924]

Before submitting a pull request, please make sure the following is done:

Checklist

• Fork the repository and create your new branch from master.
• Please mention the name of community in Pull Request title.
• Git Commit Messages
  • Use the present tense (Also in Pull Request title): "Add feature" not "Added feature"
  • Use the imperative mood (Also in Pull Request title): "Move cursor to..." not "Moves cursor to..."
  • Use rebase to squash/fixup dummy/unnecessary commits into only one commit.

[codecov]

Codecov Report

Merging #180 (13f5b78) into master (a3ffe92) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
- Coverage   80.56%   80.49%   -0.08%     
==========================================
  Files         147      147              
  Lines       11280    11280              
==========================================
- Hits         9088     9080       -8     
- Misses       1398     1403       +5     
- Partials      794      797       +3     

Impacted Files	Coverage Δ
crypto/zkproof/paillier/nth_rooot.go	86.36% <0.00%> (-4.55%)	⬇️
crypto/zkproof/paillier/blummodzkproof.go	79.62% <0.00%> (-3.71%)	⬇️
crypto/zkproof/paillier/operation_commitment.go	91.95% <0.00%> (-1.01%)	⬇️
crypto/zkproof/paillier/mulzkproof.go	90.24% <0.00%> (+2.43%)	⬆️

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