Provide functionality to detect "improper qualified access"

[ericphanson]

closes #48

I think I've got the rough functionality working:

julia> ExplicitImports.improper_qualified_names_nonrecursive(ExplicitImports)
1 issues with qualified names were found:
- `parent` has parentmodule AbstractTrees but it was accessed from ExplicitImports at /Users/eph/ExplicitImports/src/qualified_names.jl:78:21

It isn't clear to me whether or not what matters is parentmodule, which, or maybe in 1.11, ispublic... I might mark this experimental and choose to change the criteria later.

before merging, needs:

• tests
• docstring

and possibly in a followup:

• recursive variant
• check_ variant

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 90.60%. Comparing base (d46bc8e) to head (ddef68e).

Files	Patch %	Lines
src/qualified_names.jl	0.00%	44 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
- Coverage   96.47%   90.60%   -5.87%     
==========================================
  Files           5        6       +1     
  Lines         680      724      +44     
==========================================
  Hits          656      656              
- Misses         24       68      +44     

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