Move StatsItem, StatsDict, TableMetadata to dbt-common

[aranke]

Problem

Part 2 of dbt-labs/dbt-common#141, we want to move the catalog artifact schema to dbt-common so adapters can depend on them

Solution

Keep import stubs via __init__.py, but depend on versions from dbt-common.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.71%. Comparing base (d8e38c1) to head (b47b3be).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10238      +/-   ##
==========================================
+ Coverage   88.65%   88.71%   +0.05%     
==========================================
  Files         180      180              
  Lines       22477    22463      -14     
==========================================
+ Hits        19928    19929       +1     
+ Misses       2549     2534      -15     

Flag	Coverage Δ
integration	86.03% <100.00%> (+0.12%)	⬆️
unit	63.27% <100.00%> (-0.03%)	⬇️

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