fix: empty nested dynamic arrays

[tserg]

What I did

Fix #3048.

Check for empty dynamic arrays recursively.

How I did it

Add a helper function _is_empty_list to recursively determine if a literal list is empty.

How to verify it

See tests.

Commit message

fix: allow variable length empty dynamic arrays

Description for the changelog

Allow variable length empty dynamic arrays

Cute Animal Picture

[codecov-commenter]

Codecov Report

Merging #3061 (96d7b38) into master (c71b023) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 96d7b38 differs from pull request most recent head 3b54103. Consider uploading reports for the commit 3b54103 to get more accurate results

@@            Coverage Diff             @@
##           master    #3061      +/-   ##
==========================================
+ Coverage   88.35%   88.36%   +0.01%     
==========================================
  Files          97       97              
  Lines       10968    10980      +12     
  Branches     2593     2597       +4     
==========================================
+ Hits         9691     9703      +12     
  Misses        827      827              
  Partials      450      450              

Impacted Files	Coverage Δ
vyper/semantics/validation/utils.py	91.76% <100.00%> (+0.42%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more