Implement devcontainer-lock.json

[ggjulio]

See the original spec : https://github.com/devcontainers/spec/blob/main/docs/specs/devcontainer-lockfile.md

Example repo : https://github.com/microsoft/vscode/blob/main/.devcontainer/devcontainer-lock.json

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Goal

Introduce a lockfile that records the exact version, download information and checksums for each feature listed in the devcontainer.json.

This will allow for:

• Improved reproducibility of image builds (installing "latest" of a tool will still have different outcomes as the tool publishes new releases).
• Improved cachability of image builds (image cache checksums will remain stable when the lockfile pins a feature to a particular version).
• Improved security by detecting when a feature's release artifact changes after its checksum was first recorded in the lockfile ("trust on first use").

Useful resources:

• https://github.com/devcontainers/spec/issues/236
• https://github.com/devcontainers/cli/issues/564