feat(construct): merged amazon aurora vector stores

[maxtybar]

Fixes #373

1. Merged AmazonAuroraDefaultVectorStore into AmazonAuroraVectorStore resulting in a single construct that customer needs to import.
2. Created fromExistingAuroraVectorStore in AmazonAuroraVectorStore construct so customers could import values from an existing Aurora database.
3. Refactored models and moved it outside of bedrock construct in a dedicated foudnationsmodels construct. This results in elimination of potential cross-reference issues in the future where a knowledge base vector is consuming models but is also being referenced within bedrock construct.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.61%. Comparing base (d2966fb) to head (62df1b2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #418      +/-   ##
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+ Coverage   93.14%   93.61%   +0.46%     
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  Files          50       51       +1     
  Lines       11365    11614     +249     
  Branches      251      361     +110     
==========================================
+ Hits        10586    10872     +286     
+ Misses        779      742      -37     

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