feat[lang]: remove named reentrancy locks

[charles-cooper]

What I did

implement #3760

How I did it

How to verify it

Commit message

this commit removes "fine-grained" nonreentrancy locks (i.e., reentrancy
locks with names) from vyper. they aren't really used (all known
production contracts just use a single global named lock) , and in any
case such a use case should better be implemented manually by the user.

this simplifies the language and allows moderate simplification to the
storage allocator, although some complexity is added because the global
restriction has to have special handling (it cannot be handled simply in
the recursion into child modules).

refactors:
- the routine for allocating nonreentrant keys has been refactored into
  a helper function.

Description for the changelog

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[codecov-commenter]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (7bdebbf) 84.93% compared to head (c349742) 85.02%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
vyper/semantics/types/function.py	83.33%	2 Missing and 2 partials ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3769      +/-   ##
==========================================
+ Coverage   84.93%   85.02%   +0.08%     
==========================================
  Files          92       92              
  Lines       13685    13700      +15     
  Branches     3074     3074              
==========================================
+ Hits        11623    11648      +25     
+ Misses       1572     1565       -7     
+ Partials      490      487       -3     

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[pcaversaccio]

Question: I can declare variables as public in Vyper and the compiler will generate a view getter function on these functions. Example:

totalSupply: public(uint256)

Should it be possible via a kwarg to set the global nonreentrant key there as well?

totalSupply: public(uint256, nonreentrant=True)

[fubuloubu]

Question: I can declare variables as public in Vyper and the compiler will generate a view getter function on these functions. Example:

totalSupply: public(uint256)

Should it be possible via a kwarg to set the global nonreentrant key there as well?

totalSupply: public(uint256, nonreentrant=True)

This brings up a great point around flipping reentrancy locks to being the default: how would a developer be able to allow the public getter generated to be accessible to a downstream caller contract, who may need to read some properties of the calling contract (maybe in a flash loan setting)

[charles-cooper]

Question: I can declare variables as public in Vyper and the compiler will generate a view getter function on these functions. Example:

totalSupply: public(uint256)

no, you need to write your own getter (EDIT: misread the statement)

Should it be possible via a kwarg to set the global nonreentrant key there as well?

totalSupply: public(uint256, nonreentrant=True)

hmm yea, why not. i was thinking about how to handle this for other decorators like @bundle and other potential decorators in the future, so maybe this works for those as well.