chore(packages): move package folders for internal pkgs

[kuhe]

Issue

#4271

Description

move initial group of packages into internal

remaining packages:

• core - move later
• types - move later
• nested-clients - move later (codegen change is needed)
• smithy-client - move later (check if codegen change is needed)
• util-endpoints - move later (check if codegen change is needed)

Other packages will not be moved because they are known to be imported directly for other uses, including util-dynamodb.

Testing

CI

Checklist

• in followup PR - correct package homepage and directory values
• in followup PR - bump version numbers