fix(monorepo): creating packages post-Lerna@7

[achrinza]

Updates internal monorepo package creator to use npm install instead of lerna bootstrap.

This fix prevents the following error:

node ./bin/create-package.js packages/model
...
ERR! bootstrap The "bootstrap" command was removed by default in v7, and is no longer maintained.
ERR! bootstrap Learn more about this change at https://lerna.js.org/docs/legacy-package-management
 Command aborts (code 1 signal null): npx "lerna" "bootstrap" "--scope" "@loopback/model".
Error: Process 1192 exits with code 1 signal null
    at ChildProcess.<anonymous> (/home/user/Documents/git-repos/loopbackio/loopback-next/bin/create-package.js:61:11)
    at ChildProcess.emit (node:events:519:28)
    at ChildProcess._handle.onexit (node:internal/child_process:294:12)

Checklist

• [x] DCO (Developer Certificate of Origin) signed in all commits
• [x] npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• [x] Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

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