fix: constant type propagation to avoid type shadowing

[charles-cooper]

normally, type checking is idempotent, but in the case of for loop type checking, correct typechecking depends on the "type" field being fresh. this moves the type annotation to a different field which does not shadow "type".

fixes #3212

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[codecov-commenter]

Codecov Report

Merging #3213 (c0822d1) into master (8ebabc5) will decrease coverage by 33.29%.
The diff coverage is 10.00%.

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@@             Coverage Diff             @@
##           master    #3213       +/-   ##
===========================================
- Coverage   88.89%   55.61%   -33.29%     
===========================================
  Files          84       84               
  Lines       10600    10602        +2     
  Branches     2213     2148       -65     
===========================================
- Hits         9423     5896     -3527     
- Misses        769     4162     +3393     
- Partials      408      544      +136     

Impacted Files	Coverage Δ
vyper/ast/folding.py	51.26% <0.00%> (-42.02%)	⬇️
vyper/builtins/functions.py	46.79% <0.00%> (-43.69%)	⬇️
vyper/semantics/analysis/utils.py	48.99% <100.00%> (-42.98%)	⬇️

... and 65 files with indirect coverage changes

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[trocher]

Here is a minimal repro of a contract that now fails to compile with this PR:

@external
def test() -> String[12]:
    a:uint8 = 1
    return uint2str(a)

I believe the issue is that before, the annotation visitor would annotate a's type in uint2str(a) with uint8, and later, during codegen, when building the IR for uint2str(a), it was retrieved using the "shortcut" in get_possible_types_from_node but now as this shortcut as been removed, it must "recompute" the type using types_from_Name but this fails as the namespace is no longer available at this point.

[charles-cooper]

superseded by #3375