fix(cdk-assets): fails installation when new dependencies are released

[rix0rrr]

Because cdk-assets CLI depends on floating versions of dependencies, it may break when new 3rd party dependencies are released, or when it is installed just around the time a new version of AWS SDKv3 gets released (because that has hundreds of packages that all refer to each other by specific version, but they're subject to publishing/replication latency so they don't all become instantaneously available).

We used to generate a shrinkwrap file for the cdk-assets CLI but apparently that didn't work because we're still getting reports of breakage.

Instead, we'll resort to bundling the dependencies of cdk-assets into the CLI itself, so it cannot go wrong.

Because the cdk-assets package does double duty as a CLI package as well as a library package, we can't just naively stick the BundleCli job onto the package: doing that would remove all the bundled dependencies from the package.json list, which breaks its function as a library.

Instead, we're splitting the cdk-assets package in two:

• cdk-assets: will continue to contains the CLI, which will be bundled
• @aws-cdk/cdk-assets-lib: the core portion of the assets publishing, available as a library.

Because cdk-assets can no longer be used as a library, we have bumped the major version to 4 to indicate this change in API surface. In CDK pipelines we install cdk-assets@latest, so it will automatically pick up major version 4 once released.

(While this PR is strictly speaking a breaking change, I'm not adding any "breaking change" markers into the PR description, because this is changing many files across multiple packages, and I don't trust the automatic major version bumping script to not accidentally MV bump something I didn't intend to)

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[rix0rrr]

Relates to #597

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.01%. Comparing base (9d2fff5) to head (73c73a1).
⚠️ Report is 74 commits behind head on main.

Additional details and impacted files

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##             main     #603   +/-   ##
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  Coverage   79.01%   79.01%           
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  Files          46       46           
  Lines        7085     7085           
  Branches      791      791           
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  Hits         5598     5598           
  Misses       1468     1468           
  Partials       19       19           

Flag	Coverage Δ
suite.unit	79.01% <ø> (ø)

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