fix: improve GetNonce method in C#, Swift and php, and add some test code

[h-hg]

Implement GetNonce method like Java, Python or Golang.

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #336 (474da48) into master (579e973) will increase coverage by 7.20%.
The diff coverage is n/a.

❗ Current head 474da48 differs from pull request most recent head 76ec737. Consider uploading reports for the commit 76ec737 to get more accurate results

@@             Coverage Diff              @@
##             master     #336      +/-   ##
============================================
+ Coverage     82.07%   89.27%   +7.20%     
+ Complexity      224       98     -126     
============================================
  Files            21       10      -11     
  Lines          2047     1026    -1021     
  Branches         97       46      -51     
============================================
- Hits           1680      916     -764     
+ Misses          350      100     -250     
+ Partials         17       10       -7     

Flag	Coverage Δ
csharp	?
golang	95.45% <ø> (ø)
java	67.85% <ø> (ø)
php	?
python	99.39% <ø> (ø)
ts	96.22% <ø> (ø)

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see 11 files with indirect coverage changes