Pin exact versions for all npm dependencies

[desrosj]

This attempts to pin versions of npm and Composer dependencies to ensure every update to a dependency (both direct and transitive) is intentional.

This helps to guard against supply chain attacks where a vulnerable package may be installed unintentionally and unknowingly.

Reintroduce composer.lock file

Removing version ranges in favor of explicitly pinning specific versions is straightforward and does not result in any meaningful change today provided a lock file is present. However, lock file generation for Composer has been disabled in this repository since WP 6.7 (see Core-61530/r59082).

This PR proposes re-enabling lock file generation and committing the composer.lock file to version control ensuring that composer install does not install untested and unverified versions of dependencies.

Trac ticket:

Notes

• This PR currently does not update old reusable PHPUnit test workflows. Old branches should be evaluated separately as a lock file may need to be introduced for each branch.

Use of AI Tools

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

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