Support ListBlocks nested in StructBlocks

[zerolab]

A continuation of #510, this adds support for ListBlock in StrucBlock and expands the test case for ListBlock in nested StreamBlock

[codecov-commenter]

Codecov Report

Merging #525 (d380160) into main (e9e0ba9) will increase coverage by 0.00%.
The diff coverage is 89.47%.

@@           Coverage Diff           @@
##             main     #525   +/-   ##
=======================================
  Coverage   91.62%   91.63%           
=======================================
  Files          37       37           
  Lines        3201     3214   +13     
  Branches      513      515    +2     
=======================================
+ Hits         2933     2945   +12     
  Misses        152      152           
- Partials      116      117    +1     

Impacted Files	Coverage Δ
wagtail_localize/segments/extract.py	87.58% <85.71%> (-0.01%)	⬇️
wagtail_localize/test/models.py	97.46% <100.00%> (+0.06%)	⬆️

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[kaedroho]

This looks good to me, thanks!

Do you think we would need to to a similar thing for list block in nested stream blocks too?

[zerolab]

Do you think we would need to to a similar thing for list block in nested stream blocks too?

78124cc has an example of/tests for a ListBlock in a StreamBlock. I did not try ListBlock in StructBlock in StreamBlock in StreamBlock though.