fix[venom]: fix duplicate allocas

[charles-cooper]

What I did

How I did it

How to verify it

Commit message

this commit fixes a bug in the ir_node_to_venom translator. previously,
`ir_node_to_venom` tried to detect unique allocas based on
heuristics. this commit removes the heuristics and fixes the issue
in the frontend by passing through a unique ID for each variable in
the metadata. this ID is also passed into the `alloca` and `palloca`
instructions to aid with debugging. note that this results in improved
code, presumably due to more allocas being able to be reified.

this commit makes a minor change to the `sqrt()`, builtin, which is to
use `z_var.as_ir_node()` instead of `z_var.pos`, since `.as_ir_node()`
correctly tags with the alloca metadata. to be maximally conservative,
we could branch, only using `z_var.as_ir_node()` if we are using
the venom pipeline, but the change should be correct for the legacy
pipeline as well anyways.

Description for the changelog

Cute Animal Picture

[harkal]

CurveStableSwapNG-0.4.1.vy fails to compile with these changes

[cyberthirst]

apart from the misleading comment lgtm. I agree with the commit msg in that it shouldn't be necessary to introduce venom-only path. checked only the legacy version.

[HodanPlodky]

There seems to be small regression on VaultV3-0.4.0.vy codesize other then that it LGTM

[charles-cooper]

There seems to be small regression on VaultV3-0.4.0.vy codesize other then that it LGTM

i'm guessing it breaks some alias case in mem2var.. but we should get this in for correctness and work separately on mem2var

[codecov]

Codecov Report

Attention: Patch coverage is 25.58140% with 32 lines in your changes missing coverage. Please review.

Project coverage is 52.70%. Comparing base (f249c93) to head (e80f23a).
Report is 60 commits behind head on master.

Files with missing lines	Patch %	Lines
vyper/venom/ir_node_to_venom.py	7.14%	13 Missing ⚠️
vyper/venom/passes/float_allocas.py	18.75%	13 Missing ⚠️
vyper/codegen/context.py	42.85%	4 Missing ⚠️
vyper/venom/__init__.py	0.00%	1 Missing ⚠️
vyper/venom/passes/sccp/sccp.py	0.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (f249c93) and HEAD (e80f23a). Click for more details.

HEAD has 243 uploads less than BASE

Flag	BASE (f249c93)	HEAD (e80f23a)
	258	15

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4321       +/-   ##
===========================================
- Coverage   91.04%   52.70%   -38.35%     
===========================================
  Files         112      113        +1     
  Lines       16043    16061       +18     
  Branches     2698     2703        +5     
===========================================
- Hits        14607     8465     -6142     
- Misses       1001     6955     +5954     
- Partials      435      641      +206     

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