feat: add extend for dynamic arrays

[tserg]

What I did

Add extend() for dynamic arrays, partial fix for #2611.

The source dynamic array (argument) must be of dynamic array type, up to the size of the destination dynamic array.

How I did it

• Add extend_dyn_array helper to codegen/core.py.
• Add extend as member function of dynamic array type.

How to verify it

See tests

Commit message

feat: add extend for dynamic arrays

Description for the changelog

Add extend() for dynamic arrays.

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[codecov-commenter]

Codecov Report

Merging #2976 (96c680e) into master (c71b023) will increase coverage by 0.01%. The diff coverage is 97.08%.

@@            Coverage Diff             @@
##           master    #2976      +/-   ##
==========================================
+ Coverage   88.35%   88.37%   +0.01%     
==========================================
  Files          97       97              
  Lines       10968    11003      +35     
  Branches     2593     2599       +6     
==========================================
+ Hits         9691     9724      +33     
- Misses        827      828       +1     
- Partials      450      451       +1     

Impacted Files	Coverage Δ
vyper/codegen/core.py	84.26% <91.42%> (-0.93%)	:arrow_down:
vyper/builtin_functions/functions.py	90.82% <100.00%> (+0.48%)	:arrow_up:
vyper/codegen/expr.py	85.12% <100.00%> (-0.11%)	:arrow_down:
vyper/codegen/stmt.py	87.76% <100.00%> (-0.40%)	:arrow_down:
vyper/semantics/types/indexable/sequence.py	88.02% <100.00%> (+0.08%)	:arrow_up:

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[tserg]

_dynarray_make_setter should store the length, and then use a helper to copy the body.

[tserg]

this PR is shaping up, left a couple nits. thinking about whether we might want to move the dynarray method implementations into the builtins file as well? that would probably require exposing copy_dynarray_body as a public method of codegen.core though.

Cool, I think that would be neater since they are used only in vyper/builtin_functions/functions.py. Should I make the change?