feat[tool]: separate import resolution pass

[charles-cooper]

What I did

separate import resolution into its own pass

How I did it

How to verify it

Commit message

this commit separates import resolution into its own pass. there are
two reasons for this:

a) improved performance on certain operations, specifically,
computation of the integrity hash. this is a hotspot for tooling, which
needs to compute the integrity hash of a contract quickly to check if
it needs to be recompiled or not

b) logical separation. after this commit, all the I/O and filepath
computation of the module analysis is moved into its own pass, making
the module analyzer "pure" - it no longer needs to deal about input
bundles or filepaths or anything like that.

misc/refactor: this commit moves integrity hash computation into
a compiler pass. besides that, some some minor code touchups were
performed, but because of moving code into a new file, an effort
was made to keep the semantics of the code largely the same, to ease
reasoning about the diff.

Description for the changelog

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[codecov]

Codecov Report

Attention: Patch coverage is 39.49580% with 144 lines in your changes missing coverage. Please review.

Project coverage is 48.73%. Comparing base (9a208a6) to head (0716f0a).

Files with missing lines	Patch %	Lines
vyper/semantics/analysis/imports.py	35.48%	114 Missing and 6 partials ⚠️
vyper/semantics/analysis/module.py	27.58%	21 Missing ⚠️
vyper/semantics/analysis/base.py	75.00%	2 Missing ⚠️
vyper/compiler/output_bundle.py	50.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (9a208a6) and HEAD (0716f0a). Click for more details.

HEAD has 127 uploads less than BASE

Flag	BASE (9a208a6)	HEAD (0716f0a)
	140	13

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4229       +/-   ##
===========================================
- Coverage   91.35%   48.73%   -42.62%     
===========================================
  Files         109      109               
  Lines       15637    15692       +55     
  Branches     3443     3452        +9     
===========================================
- Hits        14285     7648     -6637     
- Misses        920     7438     +6518     
- Partials      432      606      +174     

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[cyberthirst]

can we name module_str as qualified_name (or qualified_module_name), which better conveys the semantics and is consistent with the previous naming?

[cyberthirst]

contains bugs as per #4268. we probably should merge and fix within the mentioned PR

[cyberthirst]

no new tests - i see that we mainly shuffled code around, but we should carefully analyze coverage before merging (we should fix the rate limits for codecov while we're at it)

[cyberthirst]

since codecov isn't working properly, I went over the coverage locally:

• no coverage (and hence the bug): https://github.com/vyperlang/vyper/pull/4229/files#diff-dc7dbf75948a3fce0db2cfa0fa819c964a534604d06f72ae88d18e3e3eef78b6R121

• no coverage (just the warning): https://github.com/vyperlang/vyper/pull/4229/files#diff-9d0f8c80ce94b689278b6516d548ea7225d2b6f3e640fcb6da0941b1209cd9c9R165

edit: fixed link