Support (very, very) basic brew-rs installs

[MikeMcQuaid]

• keep simple bottle-only brew install on the Rust path so the experimental frontend can prove out end-to-end pours before mirroring the full Ruby installer
• reuse the Rust bottle resolution and fetch flow, then call back into brew link after the pour while leaving TODO markers for relocation, dependencies, post_install, tabs, SBOMs and the remaining installer stages
• normalize API cellar values like :any_skip_relocation because the live bottle metadata uses that spelling and otherwise delegated real bottles back to Ruby

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[Copilot]

Pull request overview

Adds an initial “bottle-only” install implementation to the Rust brew-rs frontend so it can complete an end-to-end fetch → pour → link flow for very simple formulae, while delegating anything more complex back to Ruby.

Changes:

• Implement basic brew-rs install <formula>: resolve bottle, fetch it, pour it into the Cellar, remove receipt/SBOM files, then call back into Ruby brew link.
• Extend Rust formula/bottle metadata parsing to include additional install-related fields (deps, post_install_defined, service/keg-only/caveats) and propagate bottle cellar.
• Add CLI tests covering a successful basic bottle install + link, and delegation when post_install is defined.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
Library/Homebrew/rust/brew-rs/tests/cli.rs	Adds coverage for the new Rust install flow and delegation behavior.
Library/Homebrew/rust/brew-rs/src/commands/install.rs	Introduces a minimal Rust install pipeline (resolve/fetch/pour/link) with delegation gating.
Library/Homebrew/rust/brew-rs/src/commands/fetch.rs	Exposes/extends bottle+formula metadata so install can reuse Rust resolution results and check install constraints.

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