fix: support interface as constant value

[tserg]

What I did

Fix #3407

How I did it

add annotation to constant, public VariableDecl nodes

How to verify it

See tests.

Commit message

fix: support interface as constant and default value

Description for the changelog

Support interface as constant and default value

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[codecov-commenter]

Codecov Report

Merging #3411 (f928861) into master (97ff017) will decrease coverage by 17.60%.
The diff coverage is 100.00%.

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@@             Coverage Diff             @@
##           master    #3411       +/-   ##
===========================================
- Coverage   88.96%   71.36%   -17.60%     
===========================================
  Files          86       86               
  Lines       10765    10767        +2     
  Branches     2445     2445               
===========================================
- Hits         9577     7684     -1893     
- Misses        786     2465     +1679     
- Partials      402      618      +216     

Impacted Files	Coverage Δ
vyper/semantics/analysis/annotation.py	78.83% <ø> (-10.59%)	⬇️
vyper/semantics/analysis/module.py	65.19% <100.00%> (-21.44%)	⬇️

... and 54 files with indirect coverage changes

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[charles-cooper]

this looks good, will write commit message and merge in a bit