fix[lang]: typecheck hashmap indexes with folding

[DanielSchiavini]

Fixes #3984

What I did

• Updated index checks for when the subscript is folded

How I did it

• Use the reduced (i.e. folded) value when checking the index type

How to verify it

• Tests are included

Commit message

this commit fixes a bug in typechecking of folded values for hashmap
indexes. there was previously a carveout for subscript typechecking for
arrays; however, it should not apply to hashmap indexes.

this was introduced as an edge case resulting from the semantic changes
in 56c4c9dbc0. a related fix was applied in 75fb0594ab3, but it did not
handle hashmaps.

Description for the changelog

HashMap index is checked when the subscript is folded

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[Leminkay]

LGTM!

[charles-cooper]

@DanielSchiavini update the commit message please with a description of how the change was arrived at, and i'll merge

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 47.96%. Comparing base (4c66c8c) to head (93d1bb7).

:exclamation: Current head 93d1bb7 differs from pull request most recent head 19e927a. Consider uploading reports for the commit 19e927a to get more accurate results

Files	Patch %	Lines
vyper/semantics/analysis/local.py	0.00%	4 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4007 +/- ## =========================================== - Coverage 90.90% 47.96% -42.94% =========================================== Files 105 105 Lines 15246 15247 +1 Branches 3358 3358 =========================================== - Hits 13859 7313 -6546 - Misses 952 7326 +6374 - Partials 435 608 +173 ```

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